Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
GHSA-c2j3-45gr-mqc4 affects the npm package dompurify versions before 3.4.12, with 3.4.12 given as the fixed version. When a custom element is allowed through CUSTOM_ELEMENT_HANDLING.tagNameCheck, the sanitizer skips the afterSanitizeElements hook for that element, so an attribute an application strips from normal elements can remain on it. The source says this is not a direct sanitizer bypass, and it becomes exploitable only if the application's custom element later writes that preserved value into an HTML sink such as innerHTML; upgrade to dompurify 3.4.12.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.1 | Medium | 4.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N | CNA (VulnCheck) |
- CISA KEV Not listed.
- EPSS 0.0022, the 12th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 13:34 UTC First seen by agentprime
- 31 Oct 2026, 13:34 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-c2j3-45gr-mqc4
- OSV: GHSA-c2j3-45gr-mqc4
- github.com/cure53/DOMPurify/security/advisories/GHSA-c2j3-45gr-mqc4
- nvd.nist.gov/vuln/detail/CVE-2026-66010
- github.com/cure53/DOMPurify/pull/1537
- github.com/cure53/DOMPurify/commit/a9ca1e537422319a557a9a2aa61f003b23b4a197
- github.com/cure53/DOMPurify
- github.com/cure53/DOMPurify/releases/tag/3.4.12
- www.vulncheck.com/advisories/dompurify-before-hook-bypass-via-custom-element-handling