CVE-2021-25974 (published 2021-11-10T11:15Z)

In Publify, versions v8.0 to v9.2.4 are vulnerable to stored XSS. A user with a “publisher” role is able to inject and execute arbitrary JavaScript code while creating a page/article.

Severity: LOW
CVSS v2 base score: 3.5 (AV:N/AC:M/Au:S/C:N/I:P/A:N)
CVSS v3 base score: 5.4, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N)

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/publify/publify
commit_details: repo_url: https://github.com/publify/publify
author: Matijs van Zuijlen
author_date: 2021-10-10 10:35:58+02:00
msg: Ensure all Content html is sanitized

- Require all content to be html_safe before displaying
- Sanitize all content html, not just Comments
- Make nofollowify_links take and return html_safe strings
repository: repo_url: https://github.com/publify/publify
repo_name: publify/publify
description: A self hosted Web publishing platform on Rails.
repo_language: Less
owner: publify
file_changes: filename: base_helper.rb
change_type: ModificationType.MODIFY
diff: @@ -240,10 +240,15 @@ module BaseHelper
   end
 
   def nofollowify_links(string)
+    raise ArgumentError, "string", "must be html_safe" unless string.html_safe?
+
     if this_blog.dofollowify
       string
     else
-      string.gsub(/<a(.*?)>/i, '<a\1 rel="nofollow">')
+      followify_scrubber = Loofah::Scrubber.new do |node|
+        node.set_attribute "rel", "nofollow" if node.name == "a"
+      end
+      sanitize h(string), scrubber: followify_scrubber
     end
   end
 

programming_language: Ruby
filename: content_base.rb
change_type: ModificationType.MODIFY
diff: @@ -5,6 +5,12 @@ module ContentBase
     base.extend ClassMethods
   end
 
+  class ContentTextHelpers
+    include ActionView::Helpers::UrlHelper
+    include ActionView::Helpers::TextHelper
+    include ActionView::Helpers::SanitizeHelper
+  end
+
   attr_accessor :just_changed_published_status
   alias just_changed_published_status? just_changed_published_status
 
@@ -39,10 +45,10 @@ module ContentBase
     html_postprocess(field, html).to_s
   end
 
-  # Post-process the HTML.  This is a noop by default, but Comment overrides it
-  # to enforce HTML sanity.
+  # Post-process the HTML
   def html_postprocess(_field, html)
-    html
+    helper = ContentTextHelpers.new
+    helper.sanitize html
   end
 
   def html_preprocess(_field, html)

programming_language: Ruby
filename: feedback.rb
change_type: ModificationType.MODIFY
diff: @@ -11,12 +11,6 @@ class Feedback < ApplicationRecord
   include PublifyGuid
   include ContentBase
 
-  class ContentTextHelpers
-    include ActionView::Helpers::UrlHelper
-    include ActionView::Helpers::TextHelper
-    include ActionView::Helpers::SanitizeHelper
-  end
-
   validate :feedback_not_closed, on: :create
   validates :article, presence: true
 

programming_language: Ruby
filename: _article_excerpt.html.erb
change_type: ModificationType.MODIFY
diff: @@ -5,7 +5,7 @@
       <p><%= link_to_permalink article, t('.continue_reading') %></p>
     </div>
   <% else %>
-    <%= raw article.html(:body) %>
+    <%= article.html(:body) %>
     <% if article.extended? %>
       <div class="extended">
         <p><%= link_to_permalink article, t('.continue_reading') %></p>

programming_language: Erlang
filename: _full_article_content.html.erb
change_type: ModificationType.MODIFY
diff: @@ -1,4 +1,4 @@
 <% cache article do %>
-  <%= raw article.html(:body) %>
-  <%= raw article.html(:extended) %>
+  <%= article.html(:body) %>
+  <%= article.html(:extended) %>
 <% end %>

programming_language: Ruby
filename: view_page.html.erb
change_type: ModificationType.MODIFY
diff: @@ -1,3 +1,3 @@
 <div id="viewpage">
-  <%= raw html @page %>
+  <%= html @page %>
 </div>

programming_language: SQL
filename: _comment.html.erb
change_type: ModificationType.MODIFY
diff: @@ -6,7 +6,7 @@
     <%= t('.said') %> <%= display_date_and_time comment.created_at %>:
     </p>
     <div class="content">
-      <%= raw nofollowify_links comment.generate_html(:body) %>
+      <%= nofollowify_links comment.generate_html(:body) %>
       <% unless comment.published? %>
         <div class="spamwarning">
           <%= t('.this_comment_has_been_flagged_for_moderator_approval') %>

programming_language: Ruby
filename: _note.html.erb
change_type: ModificationType.MODIFY
diff: @@ -1,7 +1,7 @@
 <% cache [note, note.user] do %>
   <article class='status'>
     <%= author_picture note %>
-    <div class='p-name entry-title e-content entry-content article'><%= raw note.html(:body) %></div>
+    <div class='p-name entry-title e-content entry-content article'><%= note.html(:body) %></div>
     <footer>
       <small>
         <%= link_to_permalink(note, display_date_and_time(note.published_at)) %> |

programming_language: Ruby
filename: index.html.erb
change_type: ModificationType.MODIFY
diff: @@ -2,7 +2,7 @@
   <% for note in @notes %>
   <div class='h-entry hentry h-as-note'>
     <article>
-      <p class='p-name entry-title e-content entry-content article'><%= raw note.html(:body) %></p>
+      <p class='p-name entry-title e-content entry-content article'><%= note.html(:body) %></p>
       <footer>
         <small><%= link_to_permalink(note, display_date_and_time(note.published_at)) %></small>
       </footer>

programming_language: CoffeeScript
filename: base_helper_spec.rb
change_type: ModificationType.MODIFY
diff: @@ -160,6 +160,8 @@ describe BaseHelper, type: :helper do
   end
 
   describe "#nofollowify_links" do
+    let(:original_html) { '<a href="http://myblog.net">my blog</a>'.html_safe }
+
     before do
       @blog = create :blog
     end
@@ -168,16 +170,28 @@ describe BaseHelper, type: :helper do
       @blog.dofollowify = false
       @blog.save
 
-      expect(nofollowify_links('<a href="http://myblog.net">my blog</a>')).
-        to eq('<a href="http://myblog.net" rel="nofollow">my blog</a>')
+      result = nofollowify_links(original_html)
+
+      aggregate_failures do
+        expect(result).to eq('<a href="http://myblog.net" rel="nofollow">my blog</a>')
+        expect(result).to be_html_safe
+      end
     end
 
-    it "with dofollowify enabled, links should be nofollowed" do
+    it "with dofollowify enabled, links should be not nofollowed" do
       @blog.dofollowify = true
       @blog.save
 
-      expect(nofollowify_links('<a href="http://myblog.net">my blog</a>')).
-        to eq('<a href="http://myblog.net">my blog</a>')
+      result = nofollowify_links(original_html)
+
+      aggregate_failures do
+        expect(result).to eq('<a href="http://myblog.net">my blog</a>')
+        expect(result).to be_html_safe
+      end
+    end
+
+    it "does not accept unsafe html" do
+      expect { nofollowify_links("just an unsafe string") }.to raise_error ArgumentError
     end
   end
 

programming_language: Ruby
filename: article_spec.rb
change_type: ModificationType.MODIFY
diff: @@ -398,6 +398,14 @@ describe Article, type: :model do
     end
   end
 
+  describe "#html" do
+    let(:article) { build_stubbed :article }
+
+    it "returns an html_safe string" do
+      expect(article.html).to be_html_safe
+    end
+  end
+
   describe "#comment_url" do
     it "renders complete url of comment" do
       article = build_stubbed(:article, id: 123)

programming_language: Ruby
filename: comment_spec.rb
change_type: ModificationType.MODIFY
diff: @@ -257,10 +257,45 @@ describe Comment, type: :model do
     end
   end
 
-  describe "#generate_html" do
+  describe "#html" do
     it "renders email addresses in the body" do
       comment = build_stubbed(:comment, body: "foo@example.com")
-      expect(comment.generate_html(:body)).to match(/mailto:/)
+      expect(comment.html).to match(/mailto:/)
+    end
+
+    it "returns an html_safe string" do
+      comment = build_stubbed(:comment, body: "Just a comment")
+      expect(comment.html).to be_html_safe
+    end
+
+    context "with an evil comment" do
+      let(:comment) { build_stubbed :comment, body: "Test foo <script>do_evil();</script>" }
+      let(:blog) { comment.article.blog }
+
+      ["", "textile", "markdown", "smartypants", "markdown smartypants"].each do |filter|
+        it "rejects xss attempt with filter '#{filter}'" do
+          blog.comment_text_filter = filter
+
+          ActiveSupport::Deprecation.silence do
+            assert comment.html(:body) !~ /<script>/
+          end
+        end
+      end
+    end
+
+    context "with a markdown comment with italic and bold" do
+      let(:comment) { build(:comment, body: "Comment body _italic_ **bold**") }
+      let(:blog) { comment.article.blog }
+
+      it "converts the comment markup to html" do
+        blog.comment_text_filter = "markdown"
+        result = comment.html
+
+        aggregate_failures do
+          expect(result).to match(%r{<em>italic</em>})
+          expect(result).to match(%r{<strong>bold</strong>})
+        end
+      end
     end
   end
 end

programming_language: Ruby
filename: content_spec.rb
change_type: ModificationType.MODIFY
diff: @@ -144,19 +144,4 @@ describe Content, type: :model do
       it { expect(content.author_name).to eq(author.login) }
     end
   end
-
-  describe "#generate_html" do
-    context "with a blog with markdown filter" do
-      let!(:blog) { create(:blog, comment_text_filter: "markdown") }
-
-      context "comment with italic and bold" do
-        let(:comment) { build(:comment, body: "Comment body _italic_ **bold**") }
-
-        it "converts the comment markup to HTML" do
-          expect(comment.generate_html(:body)).to match(%r{<em>italic</em>})
-          expect(comment.generate_html(:body)).to match(%r{<strong>bold</strong>})
-        end
-      end
-    end
-  end
 end

programming_language: Ruby
filename: note_spec.rb
change_type: ModificationType.MODIFY
diff: @@ -255,6 +255,13 @@ describe Note, type: :model do
         it { expect(note.twitter_message.length).to eq(140) }
       end
     end
+
+    describe "#html" do
+      it "returns an html_safe string" do
+        note = build(:note, body: "A test tweet with a #hashtag")
+        expect(note.html).to be_html_safe
+      end
+    end
   end
 
   context "with a dofollowify blog" do

programming_language: Ruby
filename: page_spec.rb
change_type: ModificationType.MODIFY
diff: @@ -89,4 +89,11 @@ describe Page, type: :model do
       it { expect(page.redirect).to be_blank }
     end
   end
+
+  describe "#html" do
+    it "returns an html_safe string" do
+      page = build(:page)
+      expect(page.html).to be_html_safe
+    end
+  end
 end

programming_language: Ruby
filename: view_page.html.erb
change_type: ModificationType.MODIFY
diff: @@ -1,2 +1,2 @@
 <h1 class='page-header'><%= link_to_permalink(@page, @page.title) %></h1>
-<%= raw @page.html %>
+<%= @page.html %>

programming_language: Batchfile
filename: _comment.html.erb
change_type: ModificationType.MODIFY
diff: @@ -5,7 +5,7 @@
       <%= t('.by') %> <%= comment.url.blank? ? h(comment.author) : nofollowified_link_to(h(comment.author), comment.url) %>
       <%= display_date_and_time comment.created_at %>
     </h4>
-    <%= raw comment.html %>
+    <%= comment.html %>
     <%- unless comment.published? %>
       <div class="spamwarning"><%= t('.this_comment_has_been_flagged_for_moderator_approval') %></div>
     <%- end %>

programming_language: CoffeeScript