#VU54983 Stored cross-site scripting in Moodle - CVE-2021-36399

Vulnerability identifier: #VU54983

Vulnerability risk: Low

CVSSv4.0: 0.5 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-36399

CWE-ID: CWE-79

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Moodle
Web applications / Other software

Vendor: moodle.org

Description

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

The vulnerability exists due to insufficient sanitization of user-supplied data passed via the user ID number to quiz override screens. A remote user can inject and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Moodle: 3.11 - 3.11.0

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External links
https://moodle.org/mod/forum/discuss.php?d=424805
https://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-71898
https://tracker.moodle.org/browse/MDL-71898

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

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