CVE-2023-29202 (published 2023-04-15T15:15Z)

XWiki Commons are technical libraries common to several other top level XWiki projects. The RSS macro that is bundled in XWiki included the content of the feed items without any cleaning in the HTML output when the parameter `content` was set to `true`. This allowed arbitrary HTML and in particular also JavaScript injection and thus cross-site scripting (XSS) by specifying an RSS feed with malicious content. With the interaction of a user with programming rights, this could be used to execute arbitrary actions in the wiki, including privilege escalation, remote code execution, information disclosure, modifying or deleting content and sabotaging the wiki. The issue has been patched in XWiki 14.6 RC1, the content of the feed is now properly cleaned before being displayed. As a workaround, if the RSS macro isn't used in the wiki, the macro can be uninstalled by deleting `WEB-INF/lib/xwiki-platform-rendering-macro-rss-XX.jar`, where `XX` is XWiki's version, in the web application's directory.

CVSS v3 base score: 9.0, CRITICAL (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-79
cwe_name: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
description: The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
extended_description: 
            Cross-site scripting (XSS) vulnerabilities occur when:
            
               Untrusted data enters a web application, typically from a web request.
               The web application dynamically generates a web page that contains this untrusted data.
               During page generation, the application does not prevent the data from containing content that is executable by a web browser, such as JavaScript, HTML tags, HTML attributes, mouse events, Flash, ActiveX, etc.
               A victim visits the generated web page through a web browser, which contains malicious script that was injected using the untrusted data.
               Since the script comes from a web page that was sent by the web server, the victim's web browser executes the malicious script in the context of the web server's domain.
               This effectively violates the intention of the web browser's same-origin policy, which states that scripts in one domain should not be able to access resources or run code in a different domain.
            
            There are three main kinds of XSS:
            
               
                  Type 1: Reflected XSS (or Non-Persistent) - 
         			The server reads data directly from the HTTP request and reflects it back in the HTTP response. Reflected XSS exploits occur when an attacker causes a victim to supply dangerous content to a vulnerable web application, which is then reflected back to the victim and executed by the web browser. The most common mechanism for delivering malicious content is to include it as a parameter in a URL that is posted publicly or e-mailed directly to the victim. URLs constructed in this manner constitute the core of many phishing schemes, whereby an attacker convinces a victim to visit a URL that refers to a vulnerable site. After the site reflects the attacker's content back to the victim, the content is executed by the victim's browser.
               
                  Type 2: Stored XSS (or Persistent) - 
               The application stores dangerous data in a database, message forum, visitor log, or other trusted data store. At a later time, the dangerous data is subsequently read back into the application and included in dynamic content. From an attacker's perspective, the optimal place to inject malicious content is in an area that is displayed to either many users or particularly interesting users. Interesting users typically have elevated privileges in the application or interact with sensitive data that is valuable to the attacker. If one of these users executes malicious content, the attacker may be able to perform privileged operations on behalf of the user or gain access to sensitive data belonging to the user. For example, the attacker might inject XSS into a log message, which might not be handled properly when an administrator views the logs.
            
               
                  Type 0: DOM-Based XSS - 
               In DOM-based XSS, the client performs the injection of XSS into the page; in the other types, the server performs the injection. DOM-based XSS generally involves server-controlled, trusted script that is sent to the client, such as Javascript that performs sanity checks on a form before the user submits it. If the server-supplied script processes user-supplied data and then injects it back into the web page (such as with dynamic HTML), then DOM-based XSS is possible.
            
            
            Once the malicious script is injected, the attacker can perform a variety of malicious activities. The attacker could transfer private information, such as cookies that may include session information, from the victim's machine to the attacker. The attacker could send malicious requests to a web site on behalf of the victim, which could be especially dangerous to the site if the victim has administrator privileges to manage that site. Phishing attacks could be used to emulate trusted web sites and trick the victim into entering a password, allowing the attacker to compromise the victim's account on that web site. Finally, the script could exploit a vulnerability in the web browser itself possibly taking over the victim's machine, sometimes referred to as "drive-by hacking."
            In many cases, the attack can be launched without the victim even being aware of it. Even with careful users, attackers frequently use a variety of methods to encode the malicious portion of the attack, such as URL encoding or Unicode, so the request looks less suspicious.
         
         

Fix information:
repo_url: https://github.com/xwiki/xwiki-platform
commit_details: repo_url: https://github.com/xwiki/xwiki-platform
author: Michael Hamann
author_date: 2022-07-05 18:36:22+02:00
msg: XWIKI-19671: Filter the feed's content in the RSS macro
repository: repo_url: https://github.com/xwiki/xwiki-platform
repo_name: xwiki/xwiki-platform
description: The XWiki platform
repo_language: Java
owner: xwiki
file_changes: filename: pom.xml
change_type: ModificationType.MODIFY
diff: @@ -50,6 +50,11 @@
       <artifactId>xwiki-rendering-macro-box</artifactId>
       <version>${rendering.version}</version>
     </dependency>
+    <dependency>
+      <groupId>org.xwiki.commons</groupId>
+      <artifactId>xwiki-commons-xml</artifactId>
+      <version>${commons.version}</version>
+    </dependency>
     <dependency>
       <groupId>org.xwiki.platform</groupId>
       <artifactId>xwiki-platform-bridge</artifactId>

programming_language: HTML
filename: RssMacro.java
change_type: ModificationType.MODIFY
diff: @@ -22,7 +22,9 @@
 import java.io.StringReader;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 import javax.inject.Inject;
@@ -30,6 +32,7 @@
 import javax.inject.Singleton;
 
 import org.apache.commons.lang3.StringUtils;
+import org.w3c.dom.Document;
 import org.xwiki.bridge.SkinAccessBridge;
 import org.xwiki.component.annotation.Component;
 import org.xwiki.context.Execution;
@@ -49,6 +52,9 @@
 import org.xwiki.rendering.parser.Parser;
 import org.xwiki.rendering.syntax.Syntax;
 import org.xwiki.rendering.transformation.MacroTransformationContext;
+import org.xwiki.xml.html.HTMLCleaner;
+import org.xwiki.xml.html.HTMLCleanerConfiguration;
+import org.xwiki.xml.html.HTMLUtils;
 
 import com.sun.syndication.feed.synd.SyndEntry;
 import com.sun.syndication.feed.synd.SyndFeed;
@@ -102,6 +108,12 @@ public class RssMacro extends AbstractBoxMacro<RssMacroParameters>
     @Inject
     private Execution execution;
 
+    /**
+     * To clean the HTML content.
+     */
+    @Inject
+    private HTMLCleaner htmlCleaner;
+
     /**
      * Create a Feed object from a feed specified as a URL.
      */
@@ -278,13 +290,41 @@ private void generateEntries(Block parentBlock, SyndFeed feed, RssMacroParameter
                 // A case where doing this might hurt is if a feed declares "text" and has any XML inside it does
                 // not want to be interpreted as such, but displayed as is instead. But this certainly is too rare
                 // compared to mis-formed feeds that say text while they want to say HTML.
-                Block html = new RawBlock(entry.getDescription().getValue(), Syntax.XHTML_1_0);
+                Block html = new RawBlock(cleanHTML(entry.getDescription().getValue()), Syntax.HTML_5_0);
                 parentBlock.addChild(new GroupBlock(Arrays.asList(html), Collections.singletonMap(CLASS_ATTRIBUTE,
                     "rssitemdescription")));
             }
         }
     }
 
+    private String cleanHTML(String content)
+    {
+        HTMLCleanerConfiguration cleanerConfiguration = this.htmlCleaner.getDefaultConfiguration();
+        Map<String, String> parameters = new HashMap<>(cleanerConfiguration.getParameters());
+
+        // Just always use HTML 5 as this is what browsers parse.
+        parameters.put(HTMLCleanerConfiguration.HTML_VERSION, "5");
+        // Don't trust remote content.
+        parameters.put(HTMLCleanerConfiguration.RESTRICTED, "true");
+
+        cleanerConfiguration.setParameters(parameters);
+
+        Document document = this.htmlCleaner.clean(new StringReader(content), cleanerConfiguration);
+
+        // Remove the HTML envelope since this macro is only a fragment of a page which will already have an
+        // HTML envelope when rendered. We remove it so that the HTML <head> tag isn't output.
+        HTMLUtils.stripHTMLEnvelope(document);
+
+        // Don't print the XML declaration nor the XHTML DocType.
+        String cleanedContent = HTMLUtils.toString(document, true, true);
+        // Don't print the top level html element (which is always present and at the same location
+        // since it's been normalized by the HTML cleaner)
+        // Note: we trim the first 7 characters since they correspond to a leading new line (generated by
+        // XMLUtils.toString() since the doctype is printed on a line by itself followed by a new line) +
+        // the 6 chars from "<html>".
+        return cleanedContent.substring(7, cleanedContent.length() - 8);
+    }
+
     /**
      * @param romeFeedFactory a custom implementation to use instead of the default, useful for tests
      */
@@ -295,7 +335,7 @@ protected void setFeedFactory(RomeFeedFactory romeFeedFactory)
 
     /**
      * Convenience method to not have to handle exceptions in several places.
-     * 
+     *
      * @param content the content to parse as plain text
      * @return the parsed Blocks
      * @since 2.0M3

programming_language: Java
filename: feed3.xml
change_type: ModificationType.ADD
diff: @@ -0,0 +1,34 @@
+<?xml version="1.0"?>
+
+<!--
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+-->
+
+<rss version="2.0">
+  <channel>
+    <title>Test Feed 3</title>
+    <link>http://localhost/feed.xml</link>
+    <description>A pseudo-feed to test the RSS macro</description>
+    <item>
+      <title>Item1</title>
+      <link>http://localhost/blog/item1</link>
+      <description>An item with &lt;a href="javascript:alert(1)"&gt;dangerous&lt;/a&gt; &lt;b&gt;HTML&lt;/b&gt;markup.</description>
+    </item>
+  </channel>
+</rss>
\ No newline at end of file

programming_language: HTML
filename: macrorss1.test
change_type: ModificationType.MODIFY
diff: @@ -31,7 +31,7 @@ onWord [City]
 endLink [Typed = [true] Type = [url] Reference = [http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp]] [true]
 endParagraph [[class]=[rssitemtitle]]
 beginGroup [[class]=[rssitemdescription]]
-onRawText [How do Americans get ready to work with Russians aboard the International Space Station?] [xhtml/1.0]
+onRawText [<p>How do Americans get ready to work with Russians aboard the International Space Station?</p>] [html/5.0]
 endGroup [[class]=[rssitemdescription]]
 beginParagraph [[class]=[rssitemtitle]]
 beginLink [Typed = [true] Type = [url] Reference = [http://liftoff.msfc.nasa.gov/]] [true]
@@ -41,7 +41,7 @@ onWord [Exploration]
 endLink [Typed = [true] Type = [url] Reference = [http://liftoff.msfc.nasa.gov/]] [true]
 endParagraph [[class]=[rssitemtitle]]
 beginGroup [[class]=[rssitemdescription]]
-onRawText [Sky watchers in Europe, Asia, and parts of Alaska and Canada.] [xhtml/1.0]
+onRawText [<p>Sky watchers in Europe, Asia, and parts of Alaska and Canada.</p>] [html/5.0]
 endGroup [[class]=[rssitemdescription]]
 endGroup [[class]=[box rssfeed]]
 endMacroMarkerStandalone [testrss] [feed=file://feed1.xml|content=true|count=2|image=true]
@@ -49,4 +49,4 @@ endDocument
 .#-----------------------------------------------------
 .expect|xhtml/1.0
 .#-----------------------------------------------------
-<div class="box rssfeed"><img src="http://www.w3schools.com/images/logo.gif" class="wikimodel-freestanding" alt="http://www.w3schools.com/images/logo.gif"/><br/><p class="rsschanneltitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/">Lift Off News</a></span><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/"><img src="/xwiki/resources/icons/silk/feed.png" alt="/xwiki/resources/icons/silk/feed.png"/></a></span></p><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp">Star City</a></span></p><div class="rssitemdescription">How do Americans get ready to work with Russians aboard the International Space Station?</div><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/">Space Exploration</a></span></p><div class="rssitemdescription">Sky watchers in Europe, Asia, and parts of Alaska and Canada.</div></div>
\ No newline at end of file
+<div class="box rssfeed"><img src="http://www.w3schools.com/images/logo.gif" class="wikimodel-freestanding" alt="http://www.w3schools.com/images/logo.gif"/><br/><p class="rsschanneltitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/">Lift Off News</a></span><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/"><img src="/xwiki/resources/icons/silk/feed.png" alt="/xwiki/resources/icons/silk/feed.png"/></a></span></p><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp">Star City</a></span></p><div class="rssitemdescription"><p>How do Americans get ready to work with Russians aboard the International Space Station?</p></div><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/">Space Exploration</a></span></p><div class="rssitemdescription"><p>Sky watchers in Europe, Asia, and parts of Alaska and Canada.</p></div></div>
\ No newline at end of file

programming_language: Markdown
filename: macrorss2.test
change_type: ModificationType.MODIFY
diff: @@ -28,7 +28,7 @@ onWord [Item1]
 endLink [Typed = [true] Type = [url] Reference = [http://localhost/blog/item1]] [true]
 endParagraph [[class]=[rssitemtitle]]
 beginGroup [[class]=[rssitemdescription]]
-onRawText [An item with<b>HTML</b>markup.] [xhtml/1.0]
+onRawText [<p>An item with<b>HTML</b>markup.</p>] [html/5.0]
 endGroup [[class]=[rssitemdescription]]
 endGroup [[class]=[box rssfeed]]
 endMacroMarkerStandalone [testrss] [feed=file://feed2.xml|content=true|count=1|image=false]
@@ -36,4 +36,4 @@ endDocument
 .#-----------------------------------------------------
 .expect|xhtml/1.0
 .#-----------------------------------------------------
-<div class="box rssfeed"><p class="rsschanneltitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/feed.xml">Test Feed 2</a></span><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/feed.xml"><img src="/xwiki/resources/icons/silk/feed.png" alt="/xwiki/resources/icons/silk/feed.png"/></a></span></p><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/blog/item1">Item1</a></span></p><div class="rssitemdescription">An item with<b>HTML</b>markup.</div></div>
\ No newline at end of file
+<div class="box rssfeed"><p class="rsschanneltitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/feed.xml">Test Feed 2</a></span><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/feed.xml"><img src="/xwiki/resources/icons/silk/feed.png" alt="/xwiki/resources/icons/silk/feed.png"/></a></span></p><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/blog/item1">Item1</a></span></p><div class="rssitemdescription"><p>An item with<b>HTML</b>markup.</p></div></div>
\ No newline at end of file

programming_language: Lua
filename: macrorss3.test
change_type: ModificationType.MODIFY
diff: @@ -17,7 +17,7 @@ onWord [City]
 endLink [Typed = [true] Type = [url] Reference = [http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp]] [true]
 endParagraph [[class]=[rssitemtitle]]
 beginGroup [[class]=[rssitemdescription]]
-onRawText [How do Americans get ready to work with Russians aboard the International Space Station?] [xhtml/1.0]
+onRawText [<p>How do Americans get ready to work with Russians aboard the International Space Station?</p>] [html/5.0]
 endGroup [[class]=[rssitemdescription]]
 beginParagraph [[class]=[rssitemtitle]]
 beginLink [Typed = [true] Type = [url] Reference = [http://liftoff.msfc.nasa.gov/]] [true]
@@ -27,7 +27,7 @@ onWord [Exploration]
 endLink [Typed = [true] Type = [url] Reference = [http://liftoff.msfc.nasa.gov/]] [true]
 endParagraph [[class]=[rssitemtitle]]
 beginGroup [[class]=[rssitemdescription]]
-onRawText [Sky watchers in Europe, Asia, and parts of Alaska and Canada.] [xhtml/1.0]
+onRawText [<p>Sky watchers in Europe, Asia, and parts of Alaska and Canada.</p>] [html/5.0]
 endGroup [[class]=[rssitemdescription]]
 endGroup [[class]=[rssfeed]]
 endMacroMarkerStandalone [testrss] [feed=file://feed1.xml|content=true|count=2|decoration=false|encoding=UTF-8]
@@ -35,4 +35,4 @@ endDocument
 .#-----------------------------------------------------
 .expect|xhtml/1.0
 .#-----------------------------------------------------
-<div class="rssfeed"><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp">Star City</a></span></p><div class="rssitemdescription">How do Americans get ready to work with Russians aboard the International Space Station?</div><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/">Space Exploration</a></span></p><div class="rssitemdescription">Sky watchers in Europe, Asia, and parts of Alaska and Canada.</div></div>
\ No newline at end of file
+<div class="rssfeed"><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp">Star City</a></span></p><div class="rssitemdescription"><p>How do Americans get ready to work with Russians aboard the International Space Station?</p></div><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://liftoff.msfc.nasa.gov/">Space Exploration</a></span></p><div class="rssitemdescription"><p>Sky watchers in Europe, Asia, and parts of Alaska and Canada.</p></div></div>
\ No newline at end of file

programming_language: Markdown
filename: macrorss4.test
change_type: ModificationType.ADD
diff: @@ -0,0 +1,27 @@
+.runTransformations
+.#-----------------------------------------------------
+.input|xwiki/2.0
+.# Verify HTML filtering works.
+.#-----------------------------------------------------
+{{testrss feed="file://feed3.xml" content="true" count="2" decoration="false" encoding="UTF-8"/}}
+.#-----------------------------------------------------
+.expect|event/1.0
+.#-----------------------------------------------------
+beginDocument
+beginMacroMarkerStandalone [testrss] [feed=file://feed3.xml|content=true|count=2|decoration=false|encoding=UTF-8]
+beginGroup [[class]=[rssfeed]]
+beginParagraph [[class]=[rssitemtitle]]
+beginLink [Typed = [true] Type = [url] Reference = [http://localhost/blog/item1]] [true]
+onWord [Item1]
+endLink [Typed = [true] Type = [url] Reference = [http://localhost/blog/item1]] [true]
+endParagraph [[class]=[rssitemtitle]]
+beginGroup [[class]=[rssitemdescription]]
+onRawText [<p>An item with <a>dangerous</a> <b>HTML</b>markup.</p>] [html/5.0]
+endGroup [[class]=[rssitemdescription]]
+endGroup [[class]=[rssfeed]]
+endMacroMarkerStandalone [testrss] [feed=file://feed3.xml|content=true|count=2|decoration=false|encoding=UTF-8]
+endDocument
+.#-----------------------------------------------------
+.expect|xhtml/1.0
+.#-----------------------------------------------------
+<div class="rssfeed"><p class="rssitemtitle"><span class="wikiexternallink"><a class="wikimodel-freestanding" href="http://localhost/blog/item1">Item1</a></span></p><div class="rssitemdescription"><p>An item with <a>dangerous</a> <b>HTML</b>markup.</p></div></div>
\ No newline at end of file

programming_language: Lua