GHSA-2vcc-5v34-9jc8 — medium GitHub Advisory (CVE-2026-55661) in npm/tinacms

Description

TinaCMS rich-text parsing and the default link/image renderers did not sanitize the url field on Slate link/image nodes. Content containing javascript: or data:text/html URLs — including case-variant, whitespace-padded, and control-character-obfuscated forms — is rendered into href/src and executes when the content is viewed. Any actor able to author rich-text content (for example a lower-privileged editor, or imported/external content) can achieve stored XSS against editors and site viewers.

Fixed in https://github.com/tinacms/tinacms/pull/7056 via a sanitizeUrl() helper (case-insensitive, whitespace/control-character-normalized scheme allow-list) applied recursively to Slate trees at parse time and in the default rich-text rendering.

Basic information

Type: reviewed
Severity: medium
Advisory on GitHub: Open advisory ↗
Repository advisory: Open repository advisory ↗
Source code: Browse source ↗
Published (advisory): 2026-06-18 13:07:05 UTC
Updated: 2026-06-18 13:07:05 UTC
GitHub reviewed: 2026-06-18 13:07:05 UTC

CVSS Scores

Base score	Version	Severity	Vector
4.8	4.0	—	`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network. Attack complexity (AC:L) Exploitation conditions are straightforward and stable. Attack requirements (AT:N) No additional preconditions are required beyond normal reachability. Privileges required (PR:L) Low privileges are required. User interaction (UI:A) User interaction is required in an active way. Vulnerable system confidentiality impact (VC:N) No confidentiality impact on the vulnerable system. Vulnerable system integrity impact (VI:N) No integrity impact on the vulnerable system. Vulnerable system availability impact (VA:N) No availability impact on the vulnerable system. Subsequent system confidentiality impact (SC:L) Limited confidentiality impact on subsequent systems. Subsequent system integrity impact (SI:L) Limited integrity impact on subsequent systems. Subsequent system availability impact (SA:N) No availability impact on subsequent systems.

Identifiers

Type	Value
GHSA	GHSA-2vcc-5v34-9jc8 ↗
CVE	CVE-2026-55661 ↗

CWEs

CWE id	Name
CWE-79	Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-87	Improper Neutralization of Alternate XSS Syntax

Affected packages (2)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem	Package	Vulnerable range	First patched	Vulnerable functions
npm	tinacms	< 3.9.3	3.9.3	—
npm	@tinacms/mdx	< 2.1.7	2.1.7	—

TinaCMS rich-text (slatejson) rendering does not sanitize link/image URLs, allowing stored XSS via dangerous URL schemes