GHSA-W67G-2H6V-VJGQ

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.

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.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

GHSA-W67G-2H6V-VJGQ has a CVSS score of 7.1 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.1, 2.3.2, 2.2.2, 2.1.3, 2.0.2, 1.11.1); upgrading removes the vulnerable code path.

Kodem intelligence

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.

1. What is GHSA-W67G-2H6V-VJGQ? GHSA-W67G-2H6V-VJGQ is a high-severity cross-site scripting (XSS) vulnerability in phlex (rubygems), affecting versions >= 2.4.0.beta1, < 2.4.1. It is fixed in 2.4.1, 2.3.2, 2.2.2, 2.1.3, 2.0.2, 1.11.1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is GHSA-W67G-2H6V-VJGQ? GHSA-W67G-2H6V-VJGQ has a CVSS score of 7.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of phlex are affected by GHSA-W67G-2H6V-VJGQ? phlex (rubygems) versions >= 2.4.0.beta1, < 2.4.1 is affected.
4. Is there a fix for GHSA-W67G-2H6V-VJGQ? Yes. GHSA-W67G-2H6V-VJGQ is fixed in 2.4.1, 2.3.2, 2.2.2, 2.1.3, 2.0.2, 1.11.1. Upgrade to this version or later.
5. Is GHSA-W67G-2H6V-VJGQ exploitable, and should I be worried? Whether GHSA-W67G-2H6V-VJGQ is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-W67G-2H6V-VJGQ is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-W67G-2H6V-VJGQ?
   • Upgrade phlex to 2.4.1 or later
   • Upgrade phlex to 2.3.2 or later
   • Upgrade phlex to 2.2.2 or later
   • Upgrade phlex to 2.1.3 or later
   • Upgrade phlex to 2.0.2 or later
   • Upgrade phlex to 1.11.1 or later