CVE-2026-21393

Severity: medium (CVSS 4.8 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-04 · updated 2026-06-17
Weakness: CWE-79

Description

Movable Type contains a stored cross-site scripting vulnerability in Edit Comment. If crafted input is stored by an attacker, arbitrary script may be executed on a logged-in user's web browser. Note that Movable Type 7 series and 8.4 series, which are End-of-Life (EOL), are affected by the vulnerability as well.

Affected products

Six Apart Ltd. Movable Type Advanced (Software Edition): from 9.0.4 through 9.0.5 (9.0 series); from 8.8.0 through 8.8.1 (8.8 series); from 8.0.2 through 8.0.8 (8.0 series)
Six Apart Ltd. Movable Type (Cloud Edition): 9.0.5 (9 series), 8.8.1 (8 series)
Six Apart Ltd. Movable Type Premium (Advanced Edition) (Software Edition): 9.0.4 (MTP 9.0 series), 2.13 and earlier (MTP 2 series)
Six Apart Ltd. Movable Type Premium (Cloud Edition): 9.0.5 (9 series), 2.12 (MTP 2 series)
Six Apart Ltd. Movable Type Premium (Software Edition): 9.0.4 (MTP 9.0 series), 2.13 and earlier (MTP 2 series)
Six Apart Ltd. Movable Type (Software Edition): from 9.0.4 through 9.0.5 (9.0 series); from 8.8.0 through 8.8.1 (8.8 series); from 8.0.2 through 8.0.8 (8.0 series)

References

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