CVE-2026-31873
low-risk
Published 2026-03-12
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.
Do I need to act?
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0.01% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
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Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
Affected Products (1)
Unhead
Affected Vendors
References (1)
12
/ 100
low-risk
Severity
7/34 · Low
Exploitability
0/34 · Minimal
Exposure
5/34 · Minimal