# 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.

- **Severity:** Medium 4.8 (`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`)
- **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:** Yes
- **Published:** 1 Jul 2026
- **Updated:** 6 Jul 2026
- **Also known as:** GHSA-2vcc-5v34-9jc8

## 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.

Weakness: CWE-87 (Improper Neutralization of Alternate XSS Syntax), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-55661?

4 open source packages ship an affected version, including @tinacms/mdx and tinacms.


| Package | Ecosystem | 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.

## Is CVE-2026-55661 being exploited?

There is no known exploitation of CVE-2026-55661 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55661 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-55661 in the wild and no public exploit code.

Affected packages and fixed versions:
- @tinacms/mdx (npm): affected all versions; fixed in 2.1.7
- @tinacms/mdx (npm): affected all versions; fixed in 2.1.7
- tinacms (npm): affected all versions; fixed in 3.9.3
- tinacms (npm): affected all versions; fixed in 3.9.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55661/ (Markdown: https://insights.sbomify.com/CVE-2026-55661/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55661
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55661
- OSV: https://osv.dev/vulnerability/CVE-2026-55661

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55661/
Summaries are generated and may contain mistakes; the official description above is the record.