PT-2026-8392 · Rubygems · Phlex

Published 2026-02-06 · Updated 2026-02-06

OSV

CVSS v3.1

7.1

High

Base vector

AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

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
• 2.3.2
• 2.2.2
• 2.1.3
• 2.0.2
• 1.11.1

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.

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

GHSA-W67G-2H6V-VJGQ

Affected Products

Phlex

References · 8

• https://osv.dev/vulnerability/GHSA-w67g-2h6v-vjgq · Vendor Advisory
• https://github.com/yippee-fun/phlex · Note
• https://github.com/yippee-fun/phlex/security/advisories/GHSA-w67g-2h6v-vjgq · Note
• https://github.com/yippee-fun/phlex/commit/1d85da417cb15eb8cb2f54a68d531c9b35d9d03a · Note
• https://github.com/yippee-fun/phlex/commit/74e3d8610ffabc2cf5f241945e9df4b14dceb97d · Note
• https://github.com/yippee-fun/phlex/commit/556441d5a64ff93f749e8116a05b2d97264468ee · Note
• https://github.com/yippee-fun/phlex/commit/fe9ea708672f9fa42526d9b47e1cdc4634860ef1 · Note
• https://github.com/yippee-fun/phlex/commit/9f56ad13bea9a7d6117fdfd510446c890709eeac · Note