CVE-2021-3313

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-05-20 · updated 2026-06-17
Weakness: CWE-79

Description

Plone CMS until version 5.2.4 has a stored Cross-Site Scripting (XSS) vulnerability in the user fullname property and the file upload functionality. The user's input data is not properly encoded when being echoed back to the user. This data can be interpreted as executable code by the browser and allows an attacker to execute JavaScript in the context of the victim's browser if the victim opens a vulnerable page containing an XSS payload.

Affected products

Plone CMS: before 5.2.4 — fixed in 5.2.4

How to fix

Upgrade to a fixed version: Plone CMS 5.2.4. Check the vendor advisory for mitigations.

References

http://www.openwall.com/lists/oss-security/2021/05/22/1
https://plone.org/download/releases/5.2.3
https://plone.org/security/hotfix/20210518
https://www.compass-security.com/fileadmin/Research/Advisories/2021-07_CSNC-2021-013_XSS_in_Plone_CMS.txt
http://www.openwall.com/lists/oss-security/2021/05/22/1
https://plone.org/download/releases/5.2.3
https://plone.org/security/hotfix/20210518
https://www.compass-security.com/fileadmin/Research/Advisories/2021-07_CSNC-2021-013_XSS_in_Plone_CMS.txt

Get alerted when CVE-2021-3313 or the next vulnerability affects your stack