Summary
TinaCMS rich-text (slatejson) rendering does not sanitize link/image URLs, allowing stored XSS via dangerous URL schemes
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.
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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tinacms to 3.9.3 or later; @tinacms/mdx to 2.1.7 or later
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Frequently Asked Questions
- What is CVE-2026-55661? CVE-2026-55661 is a medium-severity cross-site scripting (XSS) vulnerability in tinacms (npm), affecting versions < 3.9.3. It is fixed in 3.9.3, 2.1.7. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which packages are affected by CVE-2026-55661?
tinacms(npm) (versions < 3.9.3)@tinacms/mdx(npm) (versions < 2.1.7)
- Is there a fix for CVE-2026-55661? Yes. CVE-2026-55661 is fixed in 3.9.3, 2.1.7. Upgrade to this version or later.
- Is CVE-2026-55661 exploitable, and should I be worried? Whether CVE-2026-55661 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-55661 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-55661?
- Upgrade
tinacmsto 3.9.3 or later - Upgrade
@tinacms/mdxto 2.1.7 or later
- Upgrade