CVE-2026-55661 TinaCMS rich-text (slatejson) rendering does not sanitize link/image URLs, allowing stored XSS via dangerous URL schemes
Attackers can inject malicious scripts via unsanitized URLs in rich-text content, leading to stored XSS against editors and viewers.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-55661?
CVE-2026-55661 is a medium-severity cross-site scripting vulnerability in @tinacms/mdx, published on 1 Jul 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Tina is a headless content management system. In versions prior to @tinacms/mdx 2.1.7 and tinacms 3.9.3, 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. This issue is fixed in versions @tinacms/mdx 2.1.7 and tinacms 3.9.3.
Which versions are affected by CVE-2026-55661?
4 open source packages ship an affected version, including @tinacms/mdx and tinacms.
| Package | Affected | Fixed in |
|---|---|---|
@tinacms/mdx npm | All versions | 2.1.7 |
@tinacms/mdx npm | All versions | 2.1.7 |
tinacms npm | All versions | 3.9.3 |
tinacms npm | All versions | 3.9.3 |
How do I fix CVE-2026-55661?
Upgrade @tinacms/mdx to 2.1.7 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55661 being exploited?
There is no known exploitation of CVE-2026-55661 in the wild and no public exploit code.
Sources
Also known as GHSA-2vcc-5v34-9jc8.