NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
💎
💎 RubyGems
Not in CISA KEV
HIGH severity

Phlex XSS protection bypass via attribute splatting, dynamic tags, and href valuesGHSA-w67g-2h6v-vjgq

HIGHFix: yippee-fun/phlex@1d85da4

GHSA-w67g-2h6v-vjgq is a high-severity (CVSS 7.1) vulnerability in phlex. A fix is available for phlex — see the affected versions and patch details below.

Published
Updated
Affected
6 pkgs
Patched
6 / 6
Exploits
None indexed
Exploitation data as of Feb 6, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

6 pkgs affected
💎phlex💎phlex💎phlex💎phlex💎phlex💎phlex

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Impact

During a security audit conducted with Claude Opus 4.6 and GPT-5.3-Codex, we identified three specific ways to bypass the XSS (cross-site-scripting) protection built into Phlex.

  1. The first bypass could happen if user-provided attributes with string keys were splatted into HTML tag, e.g. div(**user_attributes).
  2. The second bypass could happen if user-provided tag names were passed to the tag method, e.g. tag(some_tag_name_from_user).
  3. The third bypass could happen if user’s links were passed to href attributes, e.g. a(href: user_provided_link).

All three of these patterns are meant to be safe and all have now been patched.

Patches

Phlex has patched all three issues and introduced new tests that run against Safari, Firefox and Chrome.

The patched versions are:

Phlex has also patched the main branch in GitHub.

Workarounds

If a project uses a secure CSP (content security policy) or if the application doesn’t use any of the above patterns, it is not at risk.

Affected Packages

6 total 6 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsphlex≥ 2.4.0.beta1&&< 2.4.12.4.1bundle update phlex --conservative
💎RubyGemsphlex≥ 2.3.0&&< 2.3.22.3.2bundle update phlex --conservative
💎RubyGemsphlex≥ 2.2.0&&< 2.2.22.2.2bundle update phlex --conservative
💎RubyGemsphlex≥ 2.1.0&&< 2.1.32.1.3bundle update phlex --conservative
💎RubyGemsphlex≥ 2.0.0.beta1&&< 2.0.22.0.2bundle update phlex --conservative
💎RubyGemsphlexall versions1.11.1bundle update phlex --conservative

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phlex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update phlex to 2.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w67g-2h6v-vjgq is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact During a security audit conducted with Claude Opus 4.6 and GPT-5.3-Codex, we identified three specific ways to bypass the XSS (cross-site-scripting) protection built into Phlex. 1. The first bypass could happen if user-provided attributes with string keys were splatted into HTML tag, e.g. `div(**user_attributes)`. 2. The second bypass could happen if user-provided tag names were passed to the `tag` method, e.g. `tag(some_tag_name_from_user)`. 3. The third bypass could happen if user’s links were passed to `href` attributes, e.g. `a(href: user_provided_link)`. All three of these p
O3 Security · Impact-Aware SCA

Is GHSA-w67g-2h6v-vjgq in your dependencies?

Find it across RubyGems, including transitive dependencies.

Scan my dependencies How O3 SCA works
Phlex XSS protection bypass via attribute splatting,…