Six Apart Movable Type 8.4 Edit Comment cross site scripting

CVSS Meta Temp Score
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CTI Interest Score
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4.4$0-$5k0.00

Summaryinfo

A vulnerability was found in Six Apart Movable Type, Movable Type Advanced and Movable Type Premium 8.4. It has been declared as problematic. The impacted element is an unknown function of the component Edit Comment Handler. Such manipulation leads to cross site scripting. This vulnerability only affects products that are no longer supported by the maintainer. This vulnerability is uniquely identified as CVE-2026-21393. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Six Apart Movable Type, Movable Type Advanced and Movable Type Premium 8.4. Affected by this issue is some unknown processing of the component Edit Comment Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

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.

The advisory is shared for download at movabletype.org. This vulnerability is handled as CVE-2026-21393 since 01/29/2026. The exploitation is known to be easy. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1059.007.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Once again VulDB remains the best source for vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 4.4
VulDB Meta Temp Score: 4.4

VulDB Base Score: 3.5
VulDB Temp Score: 3.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.4
CNA Vector (jpcert): 🔒

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

01/29/2026 CVE reserved
02/04/2026 +6 days Advisory disclosed
02/04/2026 +0 days VulDB entry created
02/04/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: movabletype.org
Status: Confirmed

CVE: CVE-2026-21393 (🔒)
GCVE (CVE): GCVE-0-2026-21393
GCVE (VulDB): GCVE-100-344252

Entryinfo

Created: 02/04/2026 09:19
Changes: 02/04/2026 09:19 (75)
Complete: 🔍
Cache ID: 216::103

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