GHSA-g97x-gvcm-x72h: Mistune: XSS via unescaped class option in Admonition directive
In src/mistune/directives/admonition.py, the render_admonition() function concatenates the :class: option directly into the HTML class attribute without escaping (lines 63-68).
This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used.
The directive name parameter is safe (validated against whitelist), but the class option comes from raw user input.
Details
Original advisory: https://github.com/advisories/GHSA-g97x-gvcm-x72h
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-599260.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-59926 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
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