Medium severity · published Aug 17, 2026
CVE-2026-63670
ApostropheCMS: Mutation-XSS / allowedTags bypass via literal `</textarea/>` solidus close
6.1
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 26% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AP
apostrophe · apostrophecms
< 2.17.6 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-63670
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-63670
github.com
https://github.com/apostrophecms/apostrophe/commit/eae1fb2b72ec5d1c27d0977509c6482a0408f725
github.com
https://github.com/apostrophecms/apostrophe/pull/5501
github.com
https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-jxwj-j7wr-gfrw
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