Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
HtmlSanitizer versions below 9.0.892, and 9.1.878-beta through 9.1.892-beta, are vulnerable when the template tag is allowed. Its contents are not sanitized, so an attacker who can supply HTML to be sanitized can get script to run in the rendered page, which is a cross-site scripting risk. The default configuration is not affected because template is disallowed by default. Upgrade to 9.0.892 or 9.1.893-beta. If upgrading is not possible, keep the template tag disallowed.
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 |
|---|---|---|---|---|
| 6.3 | Medium | 4.0 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0027, the 19th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 15:22 UTC First seen by agentprime
- 31 Oct 2026, 15:22 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-j92c-7v7g-gj3f
- OSV: GHSA-j92c-7v7g-gj3f
- github.com/mganss/HtmlSanitizer/security/advisories/GHSA-j92c-7v7g-gj3f
- nvd.nist.gov/vuln/detail/CVE-2026-25543
- github.com/mganss/HtmlSanitizer/commit/0ac53dca30ddad963f2b243669a5066933d82b81
- developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/template
- github.com/mganss/HtmlSanitizer
- github.com/mganss/HtmlSanitizer/releases/tag/v9.0.892
- www.nuget.org/packages/HtmlSanitizer/9.0.892
- www.nuget.org/packages/HtmlSanitizer/9.1.893-beta