ApostropheCMS Apostrophe up to 2.17.5 HTML Sanitizer index.js sanitizeHtml HTML injection

Summaryinfo

A vulnerability, which was classified as problematic, has been found in ApostropheCMS Apostrophe up to 2.17.5. This affects the function sanitizeHtml of the file packages/sanitize-html/index.js of the component HTML Sanitizer. This manipulation causes HTML injection. The identification of this vulnerability is CVE-2026-63670. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in ApostropheCMS Apostrophe up to 2.17.5. It has been declared as problematic. Affected by this vulnerability is the function sanitizeHtml of the file packages/sanitize-html/index.js of the component HTML Sanitizer. The manipulation with an unknown input leads to a html injection vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

ApostropheCMS is an open-source Node.js content management system. Prior to 2.17.6, sanitizeHtml() can pass disallowed executable markup through packages/sanitize-html/index.js when textarea or xmp is included in allowedTags because a literal solidus after the raw-text end-tag name is treated as text by htmlparser2 and the ontext handler emits that content without escaping, while a browser parses the following img onerror markup as active HTML. This issue is fixed in version 2.17.6.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-63670 since 07/17/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 2.17.6 eliminates this vulnerability.

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Productinfo

Vendor

• ApostropheCMS

Name

• Apostrophe

Version

• 2.17.0
• 2.17.1
• 2.17.2
• 2.17.3
• 2.17.4
• 2.17.5

Website

• Product: https://github.com/apostrophecms/apostrophe/

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