Stored Cross-Site Scripting Vulnerability in Movable Type by Six Apart
CVE-2026-21393

4.8MEDIUM

Key Information:

Vendor

Six Apart Ltd.

Status
Movable Type (software Edition)
Movable Type Advanced (software Edition)
Movable Type Premium (software Edition)
Movable Type Premium (advanced Edition) (software Edition)
Vendor
CVE Published:
4 February 2026

What is CVE-2026-21393?

Movable Type is impacted by a stored cross-site scripting vulnerability found in the Edit Comment functionality. If an attacker inputs crafted data, it can be stored and later executed as arbitrary script in the web browsers of users who are logged in. This vulnerability is particularly concerning for users of the Movable Type 7 and 8.4 series, which are noted as End-of-Life (EOL), leaving them open to exploitation.

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Affected Version(s)

Movable Type (Cloud Edition) 9.0.5 (9 series)

Movable Type (Cloud Edition) 8.8.1 (8 series)

Movable Type (Software Edition) 9.0.4 to 9.0.5 (9.0 series)

References

https://movabletype.org/news/2026/02/mt-906-released.html
https://www.sixapart.jp/movabletype/news/2026/02/04-1100....
https://jvn.jp/en/jp/JVN45405689/

CVSS V4

Score:
4.8
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

CVSS V3.0

Score:
5.4
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
Required
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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