@mattkrick/sanitize-svg vulnerable to Cross-Site Scripting (XSS)
Date: 2023-01
Affected: npm/@mattkrick/sanitize-svg
Attack vector: xss
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2023-22461
CWE: CWE-79
CVSS: 7.6 (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N)

### Impact The *sanitize-svg* package uses a deny-list-pattern to sanitize SVGs to prevent cross-site scripting (XSS). In doing so, literal `<script>`-tags and on-event handlers were detected: ```typescript [...] const svgEl = div.firstElementChild! const attributes = Array.from(svgEl.attributes).map(({ name }) => name) const hasScriptAttr = !!attributes.find((attr) => attr.startsWith('on')) const scripts = svgEl.getElementsByTagName('script') return scripts.length === 0 && !hasScriptAttr ? svg : null [...] ``` There are more ways to embed JavaScript in XML files. **Anchor Tag** (requires user to click link): ```xml <svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg"> <a href="javascript:alert(document.domain)"> <text x="50" y="50" text-anchor="middle">Lauritz</text> </a> </svg> ``` **Foreign Object Tag** (no user interaction required): ```xml <svg width="500" height="500" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <text x="20" y="35">Lauritz</text> <foreignObject width="500" height="500"> <iframe xmlns="http://www.w3.org/1999/xhtml" src="javascript:confirm(document.domain);" width="400" height="250"/> </foreignObject> </svg> ``` As a result, downstream software that relies on `sanitize-svg` and expects resulting SVGs to be safe, may be vulnerable to XSS. We are aware of at least one downstream project for which this vulnerability had security implications. ### Patche


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