CVE-2023-6551: Stored XSS in class.upload.php

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-01-04 · updated 2026-06-17
Weakness: CWE-434

Description

As a simple library, class.upload.php does not perform an in-depth check on uploaded files, allowing a stored XSS vulnerability when the default configuration is used. Developers must be aware of that fact and use extension whitelisting accompanied by forcing the server to always provide content-type based on the file extension. The README has been updated to include these guidelines.

Affected products

class.upload.php: all versions

References

https://cert.pl/en/posts/2024/01/CVE-2023-6551
https://cert.pl/posts/2024/01/CVE-2023-6551
https://cert.pl/en/posts/2024/01/CVE-2023-6551
https://cert.pl/posts/2024/01/CVE-2023-6551

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