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🛡️ GHSA-w67g-2h6v-vjgq — phlex

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-79 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Phlex XSS protection bypass via attribute splatting, dynamic tags, and href values

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:

  • [2.4.1](https://rubygems.org/gems/phlex/versions/2.4.1)
  • [2.3.2](https://rubygems.org/gems/phlex/versions/2.3.2)
  • [2.2.2](https://rubygems.org/gems/phlex/versions/2.2.2)
  • [2.1.3](https://rubygems.org/gems/phlex/versions/2.1.3)
  • [2.0.2](https://rubygems.org/gems/phlex/versions/2.0.3)
  • [1.11.1](https://rubygems.org/gems/phlex/versions/1.11.1)

Phlex has also patched the [main](https://github.com/yippee-fun/phlex) 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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity low, availability none.

Weakness class

GHSA-w67g-2h6v-vjgq is classified as CWE-79: Cross-site Scripting (XSS). User-supplied data is written into a page without escaping, so attacker script runs in the browser of anyone who views it.

Affected software

GHSA-w67g-2h6v-vjgq is recorded against 1 package.

  • phlex (fixed in 1.11.1)

Timeline and source

Published on 6 February 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
github.com (Web)
github.com (Web)
github.com (Web)
github.com (Web)
github.com (Web)
github.com (Package)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
CWE CWE-79
Public Exploit ✅ No
Source OSV
Published 2026-02-06
Updated 2026-08-20
Modified 2026-02-06
Fix URL N/A

Affected Packages

Software From version Fixed in
phlex — 1.11.1

Similar Threats

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