Vulnerability identifier: #VU50903

Vulnerability risk: Low

CVSSv3.1: 5.3 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-20665

CWE-ID: CWE-79

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Movable Type
Web applications / CMS
Movable Type Advanced
Web applications / CMS
Movable Type Premium
Web applications / CMS
Movable Type Premium Advanced
Web applications / CMS

Vendor: Six Apart Ltd

Description

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data in Add asset screen of Contents field. A remote attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Movable Type: r.4705

Movable Type Advanced: r.4705

Movable Type Premium: 1.39

Movable Type Premium Advanced: 1.39

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External links
http://jvn.jp/en/jp/JVN66542874/index.html
http://movabletype.org/news/2021/02/mt-760-676-released.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.