CVE-2026-55661Network attack vector

Stored XSS via unsanitized rich-text URLs

Published Jul 1, 2026 · Updated Jul 1, 2026

Stored XSS in TinaCMS before 3.9.3 and @tinacms/mdx before 2.1.7 allows remote authenticated users to execute script in viewers' browsers. The Slate rich-text parser and default link and image renderers copy untrusted node URL values into href or src attributes without rejecting dangerous or obfuscated schemes. An actor with rich-text authoring access can store javascript or data HTML URLs that execute when an editor or site viewer opens the rendered content.

CVSS severity4.8
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in TinaCMS before 3.9.3 and @tinacms/mdx before 2.1.7 allows remote authenticated users to execute script in viewers' browsers. The Slate rich-text parser and default link and image renderers copy untrusted node URL values into href or src attributes without rejecting dangerous or obfuscated schemes. An actor with rich-text authoring access can store javascript or data HTML URLs that execute when an editor or site viewer opens the rendered content.

The record

CVE
CVE-2026-55661
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
TinaCMS
Product
@tinacms/mdx
Classifications
CWE-79, CWE-87, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.1.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

TinaCMS · @tinacms/mdxversion=< 2.1.7
TinaCMS · TinaCMSversion=< 3.9.3

Published CVSS scores

4.8GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-87Improper Neutralization of Alternate XSS Syntax
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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