GHSA-p4x4-rw2p-8j8m
HIGHGHSA-p4x4-rw2p-8j8m is a high-severity (CVSS 7.3) Cross-site Scripting (XSS) vulnerability in sanitize. O3 Security confirms whether GHSA-p4x4-rw2p-8j8m is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-site Scripting in Sanitize
Blast Radius
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Description
When HTML is sanitized using Sanitize's "relaxed" config or a custom config that allows certain elements, some content in a <math> or <svg> element may not be sanitized correctly even if math and svg are not in the allowlist.
You are likely to be vulnerable to this issue if you use Sanitize's relaxed config or a custom config that allows one or more of the following HTML elements:
iframemathnoembednoframesnoscriptplaintextscriptstylesvgxmp
Impact
Using carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize, potentially resulting in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser.
Releases
This problem has been fixed in Sanitize 5.2.1.
Workarounds
If upgrading is not possible, a workaround is to override the default value of Sanitize's :remove_contents config option with the following value, which ensures that the contents of math and svg elements (among others) are removed entirely when those elements are not in the allowlist:
%w[iframe math noembed noframes noscript plaintext script style svg xmp]
For example, if you currently use Sanitize's relaxed config, you can create a custom config object that overrides the default value of :remove_contents like this:
custom_config = Sanitize::Config.merge(
Sanitize::Config::RELAXED,
:remove_contents => %w[iframe math noembed noframes noscript plaintext script style svg xmp]
)
You would then pass this custom config to Sanitize when sanitizing HTML.
For more information
If you have any questions or comments about this advisory:
- Open an issue in the Sanitize repo.
- See Sanitize's security policy.
Credits
Many thanks to Michal Bentkowski of Securitum for reporting this bug and helping to verify the fix.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | sanitize | ≥ 3.0.0&&< 5.2.1 | 5.2.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sanitize. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update sanitize to 5.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-p4x4-rw2p-8j8m is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-p4x4-rw2p-8j8m is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-p4x4-rw2p-8j8m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-p4x4-rw2p-8j8m in your dependencies?
O3 detects GHSA-p4x4-rw2p-8j8m across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.