Vulnerability identifier: #VU51477

Vulnerability risk: Medium

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-2021-20280

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 attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data passed via feedback answer. A remote attacker can permanently inject and execute arbitrary HTML and script code in user's browser in context of vulnerable website. Note, blind SSRF attack vector is also possible in this case.

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

Moodle: 3.10.0 - 3.10.1, 3.9.0 - 3.9.4, 3.8.0 - 3.8.7, 3.7.0 - 3.7.9, 3.6.0 - 3.6.10, 3.5.0 - 3.5.16

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External links
http://moodle.org/mod/forum/discuss.php?d=419651

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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.