# CVE-2026-50290: Asymmetric Effort SpecifyJS CSS sanitization bypass in renderToString

Source: https://junglewise.ai/threats/cve-2026-50290-asymmetric-effort-specifyjs-css-sanitization-bypass-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-21. Updated: 2026-07-02  
License: CC BY 4.0 with a link back

CVE-2026-50290 · Severity: medium · CVSS 4 · Published 2026-08-21

SpecifyJS, a JavaScript library used for web development, contains a vulnerability in its server-side rendering component. An attacker could bypass security filters to inject malicious CSS code. While this primarily affects users on older web browsers (like Internet Explorer 6-10), it could potentially lead to unauthorized script execution in those environments.

Technologies: [Asymmetric Effort Specifyjs](https://junglewise.ai/threats/technologies/specifyjs), [@asymmetric-effort/specifyjs (npm)](https://junglewise.ai/threats/technologies/asymmetric-effort-specifyjs). Vendors: [Asymmetric Effort](https://junglewise.ai/threats/vendors/asymmetric-effort), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-50290 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50290 being exploited in the wild.

**How severe is CVE-2026-50290?** Medium severity, with a CVSS score of 4, published 21 August 2026.

**Which products and versions are affected?** Asymmetric Effort Specifyjs < 0.2.136; @asymmetric-effort/specifyjs (npm) < 0.2.136, SEMVER:introduced=0,fixed=0.2.136.

**Is there a fix for CVE-2026-50290?** Yes. @asymmetric-effort/specifyjs (npm): upgrade to 0.2.136 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-50290 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-50290?** Check whether you run Asymmetric Effort Specifyjs or @asymmetric-effort/specifyjs (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @asymmetric-effort/specifyjs (npm): upgrade to 0.2.136 or later

  ```sh
  npm install @asymmetric-effort/specifyjs@0.2.136
  ```


## Technical details

A Cross-Site Scripting (XSS) vulnerability exists in the `renderToString` function of `@asymmetric-effort/specifyjs` due to insufficient sanitization of CSS values. The original implementation used simple regular expressions to strip `expression(` and `url(javascript:`, which could be bypassed using CSS unicode escapes (e.g., `\65xpression(`), null bytes, or CSS comments. While modern browsers are not susceptible to these specific CSS-based execution vectors, legacy browsers (IE6-IE10) may execute the injected code. The vulnerability was fixed in version 0.2.136 by normalizing unicode escapes and stripping comments before pattern matching.

## Affected products

- asymmetric-effort @asymmetric-effort/specifyjs < 0.2.136

## Identifiers

- CVE-2026-50290
- GHSA-93q6-wwjh-jc6h

## Timeline

- 2026-05-29: disclosed: Vulnerability identified during penetration test code review
- 2026-05-29: patched: Fixed in version 0.2.136
- 2026-07-02: advisory: GitHub Advisory published

## References

- [https://github.com/asymmetric-effort/specifyjs/security/advisories/GHSA-93q6-wwjh-jc6h](https://github.com/asymmetric-effort/specifyjs/security/advisories/GHSA-93q6-wwjh-jc6h)
- [https://github.com/asymmetric-effort/specifyjs/commit/25d1fb491d99479efdf501f5f75e0bb80c908f0a](https://github.com/asymmetric-effort/specifyjs/commit/25d1fb491d99479efdf501f5f75e0bb80c908f0a)
- [https://api.github.com/repos/asymmetric-effort/specifyjs/security-advisories/GHSA-93q6-wwjh-jc6h](https://api.github.com/repos/asymmetric-effort/specifyjs/security-advisories/GHSA-93q6-wwjh-jc6h)

## Related threats

- [SpecifyJS SSRF via URL validation bypass in secure-fetch](https://junglewise.ai/threats/cve-2026-50288-specifyjs-ssrf-via-url-validation-bypass-in-secure-fetch)
- [@asymmetric-effort/specifyjs redirect SSRF in secureFetch](https://junglewise.ai/threats/asymmetric-effort-specifyjs-redirect-ssrf-in-securefetch-09dbb315)
- [@asymmetric-effort/specifyjs unrestricted data URI memory exhaustion](https://junglewise.ai/threats/asymmetric-effort-specifyjs-unrestricted-data-uri-memory-exhaustion-47844f22)
- [@asymmetric-effort/specifyjs localhost bypass in SSRF check](https://junglewise.ai/threats/asymmetric-effort-specifyjs-localhost-bypass-in-ssrf-check-63583c44)
- [@asymmetric-effort/specifyjs information disclosure via console warnings](https://junglewise.ai/threats/asymmetric-effort-specifyjs-information-disclosure-via-console-warnings-1afedf35)