CVE-2026-31873
MEDIUM WAF: High
CVSS 6.1
Published: 2026-03-12
CWE-79
Unhead is a document head and template manager. Prior to 2.1.11, The link.href check in makeTagSafe (safe.ts) uses String.includes(), which is case-sensitive. Browsers treat URI schemes case-insensitively. DATA:text/css,... is the same as data:text/css,... to the browser, but 'DATA:...'.includes('data:') returns false. An attacker can inject arbitrary CSS for UI redressing or data exfiltration via CSS attribute selectors with background-image callbacks. This vulnerability is fixed in 2.1.11.
WAF Coverage Analysis
Cross-Site Scripting (XSS)
High WAF Coverage
OWASP: A03:2021 Injection
941xxx - XSS / XXE
Affected Software
| Vendor | Product | Version |
|---|---|---|
| unjs | unhead | up to 2.1.11 |
References
- github.com (Exploit, Mitigation, Vendor Advisory)