🚨 [security] Update loofah 2.25.1 → 2.25.2 (patch)

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🚨 Your current dependencies have known security vulnerabilities 🚨

This dependency update fixes known security vulnerabilities. Please see the details below and assess their impact carefully. We recommend to merge and deploy this as soon as possible!

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Here is everything you need to know about this update. Please take a good look at what changed and the test results before merging this pull request.

What changed?

↗️ loofah (indirect, 2.25.1 → 2.25.2) · Repo · Changelog

Security Advisories 🚨

🚨 Loofah `allowed_uri?` does not detect `javascript:` URIs split by named whitespace character references

Summary

Loofah::HTML5::Scrub.allowed_uri? does not correctly reject javascript: URIs when the scheme is split or prefixed by the HTML5 named character references 	 (tab) or 
 (line feed).

This is a bypass of the fix for GHSA-46fp-8f5p-pf2m, which handled the equivalent numeric character references (	, 
, 
) but did not cover the named forms.

Details

allowed_uri? decodes HTML entities with CGI.unescapeHTML, which handles numeric character references but not HTML5 named character references. Payloads like java	script:alert(1) are therefore left intact, so the method does not recognize the javascript: scheme and returns true. A browser, however, decodes 	 and 
 to tab and line feed and strips them from the URL during parsing, producing javascript:alert(1).

	 and 
 are the only relevant named character references: across the HTML5 named-character table, they are the only two that decode to characters the WHATWG URL parser strips from a URL (U+0009 and U+000A; there is no named reference for U+000D).   /   decode to U+00A0, which browsers do not strip, so they aren't usable for this bypass.

Note that Loofah's default sanitize() path is not affected, because Nokogiri decodes or entity-escapes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects callers of the public allowed_uri? string-level helper that pass it HTML-encoded strings.

Impact

Callers that validate a user-controlled URL with Loofah::HTML5::Scrub.allowed_uri? and then render the approved value into an href or other browser-interpreted URI attribute may be vulnerable to cross-site scripting (XSS). This includes applications that call allowed_uri? directly, as well as higher-level features built on top of it, such as Action Text 8.2's markdown link validation.

Mitigation

Upgrade to Loofah >= 2.25.2.

Credit

Responsibly reported by GitHub user @connorshea.

🚨 Loofah: SVG `href` attribute bypasses local-reference restriction

Summary

Loofah's HTML5 sanitizer restricted only the xlink:href attribute on certain SVG elements to local, same-document references. Browsers also accept a plain href attribute as an alternative to the deprecated xlink:href per the SVG 2 spec, but Loofah did not apply the same restriction to it, allowing those elements to reference arbitrary external documents.

Impact

SVG <use> can load and render external SVG content by reference. If the referenced external SVG is same-origin and contains scripts or other dangerous content, it could execute in the context of the sanitized document. <feImage> can load external images, which can be used for tracking. Modern browsers restrict cross-origin <use> fetches, which limits but does not eliminate the risk.

Applications that sanitize user-supplied SVG (directly, or as part of HTML) with Loofah's default allowlist are affected.

Mitigation

Upgrade to Loofah >= 2.25.2.

Credit

Found by the maintainer, Mike Dalessio, during a security audit.

🚨 Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons

Summary

Loofah::HTML5::Scrub.allowed_uri? does not correctly reject javascript: or vbscript: URIs when the scheme is split by a numeric character reference that has no trailing semicolon. A browser decodes such references and resolves the URL to an executable javascript: scheme, while allowed_uri? reports it safe.

This is a bypass of the fix for GHSA-46fp-8f5p-pf2m, which handled numeric character references with a trailing ; (	, 
, 
) but did not cover the forms without semicolons.

Details

allowed_uri? decodes HTML entities with CGI.unescapeHTML, which decodes numeric character references only when they carry a trailing ;. A reference without a semicolon such as &#58 (colon) or &#9 (tab) is left literal, so the scheme-detection check finds no scheme, and the method falls through to its scheme-less path and returns true.

A browser, however, decodes numeric character references even without a trailing semicolon. An encoded colon such as &#58 becomes the : scheme separator, so javascript&#58alert(1) resolves to javascript:alert(1). Encoded whitespace such as &#9 (tab) is decoded and then stripped from the URL, rejoining the surrounding text, so java&#9script:alert(1) also resolves to javascript:alert(1). In both cases the URL executes while allowed_uri? approved it as safe.

Note that Loofah's default sanitize() path is not affected, because Nokogiri decodes or entity-escapes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects callers of the public allowed_uri? string-level helper that pass it HTML-encoded strings.

Impact

Callers that validate a user-controlled URL with Loofah::HTML5::Scrub.allowed_uri? and then render the approved value into an href or other browser-interpreted URI attribute may be vulnerable to cross-site scripting (XSS). This includes applications that call allowed_uri? directly, as well as higher-level features built on top of it, such as Action Text 8.2's markdown link validation.

Mitigation

Upgrade to Loofah >= 2.25.2.

Credit

Responsibly reported by GitHub user @MoonFuji.

Release Notes

2.25.2

2.25.2 / 2026-07-15

Security

• Ensure Loofah::HTML5::Scrub.allowed_uri? recognizes numeric character references without semicolons (e.g. javascript&#58alert(1)), which browsers decode and execute, and rejects schemes split by them. See GHSA-5qhf-9phg-95m2. @flavorjones
• Ensure Loofah::HTML5::Scrub.allowed_uri? recognizes the named character references 	 and 
, which CGI.unescapeHTML does not decode and browsers strip from URIs, and rejects schemes split by them (e.g. java	script:alert(1)). See GHSA-8whx-365g-h9vv. @flavorjones
• Ensure that both href and xlink:href attributes on SVG elements like use are restricted to local (same-document) references. Previously only xlink:href was restricted, allowing the SVG 2 href attribute to reference external documents. See GHSA-9wjq-cp2p-hrgf. @flavorjones

Improved

• Harden data: URI mediatype parsing in Loofah::HTML5::Scrub.allowed_uri?. The mediatype is now parsed following the WHATWG data: URL spec and RFC 2397 instead of simply being split on a colon. A data: URI with an omitted or malformed mediatype is now treated as text/plain and allowed, and one without the required comma is now rejected. #305 @flavorjones
• Remove feed from the default set of allowed protocols. The feed URI scheme was never accepted as a standard protocol, and no major browser supports it. Removing it reduces the attack surface particularly for non-browser contexts. #304 @flavorjones
• Remove a vestigial &#x70 alternative from Loofah::HTML5::SafeList::PROTOCOL_SEPARATOR. This appears to be an ancient typo dating back to pre-extraction Rails circa 2007. #305 @flavorjones

Does any of this look wrong? Please let us know.

Commits

See the full diff on Github. The new version differs by 14 commits:

• version bump to v2.25.2
• Merge pull request #308 from flavorjones/security-2252
• Update `allowed_uri?` to decode semicolon-less numeric character references
• Update `allowed_uri?` to handle named whitespace character references
• Properly restrict SVG href attributes
• test: opt into JSON comment parsing for sanitizer testdata (#307)
• test: do not run in verbose mode
• doc: update CHANGELOG
• Merge pull request #305 from flavorjones/drop-protocol-typo
• version bump to 2.25.2.beta1
• Harden `data:` URI mediatype parsing
• Remove `&#x70` from PROTOCOL_SEPARATOR
• Merge pull request #304 from flavorjones/drop-feed-protocol
• Remove `feed` from the default allowed protocols

↗️ crass (indirect, 1.0.6 → 1.0.7) · Repo · Changelog

Release Notes

1.0.7

Security

• High: Fixed a denial of service vulnerability in which a large numeric exponent could consume disproportionate CPU and memory before the value was clamped. Exponents are now bounded before 10**exponent is computed. (GHSA-6wmf-3r64-vcwv)

• Moderate: Fixed a scenario in which deeply nested simple blocks or functions could exhaust the Ruby stack and raise SystemStackError, or could result in excessive memory usage. Parser nesting is now limited to a configurable maximum depth via a new option (:maximum_depth, with a conservative default of 25). Constructs nested more deeply are discarded as an :error node with the value "maximum-depth-exceeded". (GHSA-6jxj-px6v-747w)

• Moderate: Fixed a scenario in which a long run of adjacent comments could exhaust the Ruby stack and raise SystemStackError. Discarded comments are now skipped iteratively rather than recursively. (GHSA-wwpr-jff3-395c)

• Moderate: Fixed a denial of service vulnerability in which inputs containing many non-ASCII characters could cause excessive CPU usage due to inefficient handling of multi-byte characters during tokenization. (GHSA-8vfg-2r28-hvhj)

Does any of this look wrong? Please let us know.

Commits

See the full diff on Github. The new version differs by 26 commits:

• Release 1.0.7
• Fix inefficient handling of non-ASCII characters during tokenization
• Prevent a long run of adjacent comments from exhausting the stack
• Limit recursion depth to prevent stack overflow and memory exhaustion
• Prevent resource exhaustion denial of service via excessively large exponents
• Bump version to 1.0.7
• Update CI workflow dependencies
• Update CI test matrix
• Upgrade minitest and rake
• Merge pull request #18 from stoivo/main
• Update links to point to the targeted version
• name Test name look a bit nicer
• Upgrade minitest to 5.21.1
• Use actions/checkout@v4
• Add Ruby 3.2.x to the test matrix
• Merge pull request #13 from voxik/minitest519
• Fix compatibility with Minitest 5.19+
• Remove redundant Ruby 3.2 from the CI matrix
• Add Ruby 3.1 and 3.2 to the CI matrix.
• Remove 1.9.3 and truffleruby from the test matrix
• Replace Travis with GitHub Actions
• Reformat readme and history
• Remove copyright year
• Require mfa
• Upgrade dev dependencies
• 🎨

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