CVE-2021-20813

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-08-26 · updated 2026-06-17
Weakness: CWE-79

Description

Cross-site scripting vulnerability in Edit screen of Content Data of Movable Type (Movable Type 7 r.4903 and earlier (Movable Type 7 Series) and Movable Type Advanced 7 r.4903 and earlier (Movable Type Advanced 7 Series)) allows remote attackers to inject arbitrary script or HTML via unspecified vectors.

Affected products

Six Apart Ltd. Movable Type: from 7.0 before 7.8.0 — fixed in 7.8.0

How to fix

Upgrade to a fixed version: Six Apart Ltd. Movable Type 7.8.0. Check the vendor advisory for mitigations.

References

https://jvn.jp/en/jp/JVN97545738/index.html
https://movabletype.org/news/2021/08/mt-780-681-released.html
https://jvn.jp/en/jp/JVN97545738/index.html
https://movabletype.org/news/2021/08/mt-780-681-released.html

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