Update dependency svgo to v4.0.2 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
svgo (source)	4.0.0 → 4.0.2

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SVGO DoS through entity expansion in DOCTYPE (Billion Laughs)

CVE-2026-29074 / GHSA-xpqw-6gx7-v673

More information

Details

Summary

SVGO accepts XML with custom entities, without guards against entity expansion or recursion. This can result in a small XML file (811 bytes) stalling the application and even crashing the Node.js process with JavaScript heap out of memory.

Details

The upstream XML parser (sax) doesn't interpret custom XML entities by default. We pattern matched custom XML entities from the DOCTYPE, inserting them into parser.ENTITIES, and enabled unparsedEntities. This gives us the desired behavior of supporting SVGs with entities declared in the DOCTYPE.

However, entities can reference other entities, which can enable small SVGs to explode exponentially when we try to parse them.

Proof of Concept

import { optimize } from 'svgo';

/** Presume that this string was obtained in some other way, such as network. */
const original = `
  <?xml version="1.0"?>
  <!DOCTYPE lolz [
  <!ENTITY lol "lol">
  <!ELEMENT lolz (#PCDATA)>
  <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
  <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
  <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
  <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
  <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
  <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
  <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
  <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
  <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
  ]>
  <lolz>&lol9;</lolz>
`;

optimize(original);

Impact

If SVGO is run on untrusted input (i.e., user uploaded to server-side application), then the untrusted SVG can effectively stall or crash the application with an SVG < 1 KB in size.

It's unlikely to impact users who just use SVGO locally on their own SVGs or in build pipelines.

Patches

SVGO has patched v4.0.1, v3.3.3, and v2.8.1! However, it's strongly recommended to upgrade to v4 regardless, as previous versions are not officially supported anymore.

Workarounds

== 4.0.0

For v4, users do not specifically have to upgrade SVGO, though it is recommended to do so. A package manager can be used to upgrade sax recursively:

For example:

yarn up -R sax

New options were introduced upstream which makes the way SVGO parses SVGs safe by default.

>= 2.1.0, <= 3.3.2

Users of v3 and v2 will have to take manual action. If users can't upgrade, they may be able to work around this as long as the project doesn't require support for custom XML entities, though it's not a simple flag.

Parse the DOCTYPE directly and check for the presence of custom entities. If entities are present, throw/escape before passing them to SVGO.

+ import SAX from 'sax';
  import { optimize } from 'svgo';

- const original =`
+ let original = `
    <?xml version="1.0"?>
    <!DOCTYPE lolz [
    <!ENTITY lol "lol">
    <!ELEMENT lolz (#PCDATA)>
    <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
    <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
    <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
    <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
    <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
    <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
    <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
    <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
    <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
    ]>
    <lolz>&lol9;</lolz>
  `;

+ const parser = SAX.parser();
+ /** @param {string} doctype */
+ parser.ondoctype = (doctype) => {
+   original = original.replace(doctype, '');
+ }
+ parser.write(original);

  optimize(original);

Resources

• Wikipedia: Billion laughs attack

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

• https://github.com/svg/svgo/security/advisories/GHSA-xpqw-6gx7-v673
• https://nvd.nist.gov/vuln/detail/CVE-2026-29074
• https://github.com/advisories/GHSA-xpqw-6gx7-v673

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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SVGO removeScripts plugin leaves some executable scripts intact

GHSA-2p49-hgcm-8545

More information

Details

Summary

SVGO's removeScripts plugin (disabled by default) removes scripts from the SVG, however executable scripts were left intact in some cases. If a consumer relied on this plugin for sanitization and served them to users, these SVGs could open up doors to XSS.

Details

SVGO has a plugin for removing scripts from an SVG, which removes:

• <script> elements
• JavaScript URIs (v4 and v3 only)
• on… event handlers (v4 and v3 only)

While SVGO is not a sanitization library, SVGO continues to maintain the plugin for those already using it for this purpose.

However, there were two problems:

• SVGO did not check namespaced/prefixed script elements, for example if one declared an explicit prefix for the SVG namespace ( <svg:script>) instead of using the default namespace ( <script>), the <svg:script> tag would be left intact.
• SVGO case sensitively matched JavaScript URIs, but it should've been case-insensitive.

Proof of Concept

import { optimize } from 'svgo';

/** Presume that this string was obtained in some other way, such as network. */
const original = `
  <svg xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg" xmlns:uwu="http://www.w3.org/1999/xlink" viewBox="0 0 100 100" version="1.1">
    <a uwu:href="JavaScript:(() =&gt; { alert(document.cookie) })();"><text y="30">uwu</text></a>
    <svg:script>
      alert(document.cookie);
    </svg:script>
  </svg>
`;

optimize(original, {
  plugins: ['removeScripts']
});
// Did not remove <svg:script> or uwu:href="JavaScript:…—still executed by browsers.

Impact

If you run SVGO on untrusted input (e.g., user uploads to a web application) and you depended on removeScripts, then some scripts may still be present. If that SVG was then opened directly by another user on the same domain, it could invoke scripts that could read local storage or cookies.

This may affect you if you have enabled one of the following:

SVGO Version	Plugin Name
v4	removeScripts
v3	removeScriptElement
v2	removeScriptElement
v1	removeScriptElement

It's unlikely to impact users who just use SVGO locally on their own SVGs or in build pipelines.

Patches

>= 3.0.0, <= 4.0.1

SVGO patched v4.0.2 and v3.3.4. Just upgrade the dependency using your preferred package manager! For example:

yarn up svgo

##### or if SVGO is a nested dependency
yarn up -R svgo

The proposed fix is to improve our namespace-aware handling to explicitly act on the default namespace, SVG namespace, and XHTML namespace only. This handles all scripts that are executed by browsers, but will leave intact custom prefixes that happen to have an element called <*:script> which clients shouldn't treat as executable.

>= 2.0.0, <= 2.8.2

SVGO patched v2.8.3, however SVGO v2 explicitly only implements and documents that it will remove <script> elements and nothing more. It has the namespace aware handling for tags like <svg:script> or <xhtml:script>, but has not been updated to remove JavaScript URIs or event handlers like >= v3. If this is something you need, please upgrade to v4 or v3, or reach for one of the documented workarounds at the end.

>= 1.0.0, <= 1.3.2

SVGO v1 has been deprecated for a while now and won't be patched. Please upgrade to a more recent version! If something is preventing you from doing so, please reach out! We're happy to expand our migration guides or support you if you're having trouble.

Workarounds

If your motivation for enabling the plugin is SVG sanitization, consider reaching for a dedicated SVG sanitization tool and invoke it before passing the SVG to SVGO.

Severity

• CVSS Score: 8.2 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

References

• https://github.com/svg/svgo/security/advisories/GHSA-2p49-hgcm-8545
• https://github.com/svg/svgo/commit/628e3bc7336625a30365d0a9b60185307d852466
• https://github.com/svg/svgo/commit/72a23886b4698b27624b936f3a15a80afd36d75f
• https://github.com/svg/svgo/commit/f529cfccc6c154d6f6eabe276ec637a8c5db6763
• https://github.com/svg/svgo/releases/tag/v2.8.3
• https://github.com/svg/svgo/releases/tag/v3.3.4
• https://github.com/svg/svgo/releases/tag/v4.0.2
• https://github.com/advisories/GHSA-2p49-hgcm-8545

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

svg/svgo (svgo)

v4.0.2

Compare Source

What's Changed

Security

• removeScripts, remove JavaScript URIs case-insensitively and make <script> handling namespace aware. By @​SethFalco

Bug Fixes

• convertColors, skip case-normalization for CSS custom properties. By @​SethFalco in #​2213
• convertPathData, improve handling of consecutive t commands. By @​KTibow in #​2156
• convertPathData, safer handling of paths. By @​KTibow in #​2158
• Improve parsing of negative (or +) arc radii. By @​KTibow in #​2205
• When converting to a data URI, only encode it as a data URI once. By @​johnkenny54 in #​2053

Performance

• mergePaths, speed up child node removal. By @​mozzie in #​2216

Other Changes

• removeAttributesBySelector, log warning and noop if missing parameters. By @​KTibow in #​2215

v4.0.1

Compare Source

What's Changed

Dependencies

• Sets minimum version of sax (XML parser) to v1.5.0, which improves built-in guards against entity expansion.

Bug Fixes

• removeEmptyContainers, removed leftover <use> elements referencing an empty container that were removed. By @​johnkenny54 in #​2051
• removeUnknownsAndDefaults, don't remove attributes if they're referenced in attribute selectors (CSS). By @​SethFalco in #​2144

Performance

• convertPathData, refactor to reduce redundant equality checks. By @​Lorfdail in #​1764 and #​2135
• removeHiddenElems, compute styles lazily. By @​Lorfdail in #​1764 and #​2135

Other Changes

• Plugins no longer include if they are enabled or disabled by default, as this was written inconsistently. The --show-plugins argument appends the presets a plugin is in to the end of the line. By @​viralcodex in #​2174
• Plugin/preset types to enforce the name start with preset- if it is a preset (collection of plugins). By @​SethFalco in #​2178

Metrics

Before and after of the browser bundle of each respective version:

	v4.0.0	v4.0.1	Delta
svgo.browser.js	780.2 kB	781.5 kB	⬆️ 1.3 kB

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