CVE-2026-63670

ApostropheCMS: Mutation-XSS / allowedTags bypass via literal `</textarea/>` solidus close

MEDIUM
6.1
CVSS Score
Published: August 17, 2026 at 07:49 PM UTC
Updated: October 23, 2026 at 04:10 PM UTC
1 product affected across 1 vendorApostrophecms

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.3%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2.17.6
Affected range stops below 2.17.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.1MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79

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