CVE-2026-65900
DOMPurify before 3.4.8 Template Expression Injection via RETURN_DOM
Blast Radius
dompurifyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
DOMPurify versions >=3.0.0 and before 3.4.8, when configured with SAFE_FOR_TEMPLATES together with a DOM output mode (RETURN_DOM, RETURN_DOM_FRAGMENT, or IN_PLACE), fail to strip template expressions (e.g. ${evil}, {{evil}}, <%evil%>) inside <template> element content. The final normalization/scrub pass (_scrubTemplateExpressions) uses a NodeIterator and node.normalize() that do not descend into template.content, so expressions that only form after adjacent text nodes merge survive sanitization. This bypasses SAFE_FOR_TEMPLATES and can allow a downstream template engine to evaluate attacker-supplied expressions. The string output path is not affected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | dompurify | ≥ 3.0.0&&< 3.4.8 | 3.4.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dompurify. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update dompurify to 3.4.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-65900 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-65900 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-65900. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-65900 in your dependencies?
O3 detects CVE-2026-65900 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.