What’s Vulnerable › Vulnerabilities

CVE-2023-23921: Moodle: reflected xss risk in some returnurl parameters

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-02-17 · updated 2026-06-17
• Weakness: CWE-79

Description

The vulnerability was found Moodle which exists due to insufficient sanitization of user-supplied data in some returnurl parameters. 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. This flaw allows a remote attacker to perform cross-site scripting (XSS) attacks.

Affected products

• Moodle: from 3.9.0 before 3.9.19; from 3.11.0 before 3.11.12; from 4.0.0 before 4.0.6; 4.1.0 — fixed in 3.11.12, 3.9.19, 4.0.6

How to fix

Upgrade to a fixed version: Moodle 3.11.12, 3.9.19, 4.0.6. Check the vendor advisory for mitigations.

References

• http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-76810
• https://bugzilla.redhat.com/show_bug.cgi?id=2162526
• https://moodle.org/mod/forum/discuss.php?d=443272#p1782021
• http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-76810
• https://bugzilla.redhat.com/show_bug.cgi?id=2162526
• https://moodle.org/mod/forum/discuss.php?d=443272#p1782021

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