CVE-2020-4049: Authenticated self-XSS via theme uploads in WordPress

Severity: low (CVSS 2.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-06-12 · updated 2026-06-17
Weakness: CWE-80

Description

In affected versions of WordPress, when uploading themes, the name of the theme folder can be crafted in a way that could lead to JavaScript execution in /wp-admin on the themes page. This does require an admin to upload the theme, and is low severity self-XSS. This has been patched in version 5.4.2, along with all the previously affected versions via a minor release (5.3.4, 5.2.7, 5.1.6, 5.0.10, 4.9.15, 4.8.14, 4.7.18, 4.6.19, 4.5.22, 4.4.23, 4.3.24, 4.2.28, 4.1.31, 4.0.31, 3.9.32, 3.8.34, 3.7.34).

Affected products

Debian Linux: 8.0, 9.0, 10.0
Fedoraproject Fedora: 31, 32
WordPress: from 3.7 before 3.7.34; from 3.8 before 3.8.34; from 3.9 before 3.9.32; from 4.0 before 4.0.31; from 4.1 before 4.1.31; from 4.2 before 4.2.28 — fixed in 3.7.34, 3.8.34, 3.9.32, 4.0.31, 4.1.31, 4.2.28

How to fix

Upgrade to a fixed version: WordPress 3.7.34, 3.8.34, 3.9.32, 4.0.31. Check the vendor advisory for mitigations.

References

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