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

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).

Published: 2020-06-12 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-4049 is rated Low Risk (36.1/100): CVSS Low severity, with medium exploitation likelihood (EPSS 2.80%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-4049

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 5.89% 2.80% -3.08%
2 2026-03-04 6.30% 5.89% -0.41%
3 2026-03-01 — 6.30% —

Full EPSS history (42 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-4049

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
2.4 3.1 LOW
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 0.9 1.4 [email protected]
2.4 3.1 LOW
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 0.9 1.4 [email protected]
3.5 2.0 LOW
AV:N/AC:M/Au:S/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 6.8 2.9 [email protected]

Weakness enumeration for CVE-2020-4049

OS Trackers for CVE-2020-4049

vendor priority summary link
debian not yet assigned CVE-2020-4049 not yet assigned priority: Debian including 1 source packages (wordpress), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-4049
ubuntu low CVE-2020-4049 low priority: Ubuntu including 1 source packages (wordpress), 17 status rows across 17 suites (bionic, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 6, ignored 5, needs-triage 4, DNE 1, released 1. https://ubuntu.com/security/CVE-2020-4049

Affected software / configurations for CVE-2020-4049

Vendor Product Version Raw CPE
wordpress wordpress >= 3.7, < 3.7.34 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 3.8, < 3.8.34 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 3.9, < 3.9.32 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.0, < 4.0.31 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.1, < 4.1.31 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.2, < 4.2.28 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.3, < 4.3.24 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.4, < 4.4.23 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.5, < 4.5.22 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.6, < 4.6.19 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.7, < 4.7.18 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.8, < 4.8.14 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 4.9, < 4.9.15 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 5.0, < 5.0.10 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 5.1, < 5.1.6 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 5.2, < 5.2.7 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 5.3.0, < 5.3.4 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
wordpress wordpress >= 5.4, < 5.4.2 cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

References for CVE-2020-4049

URL Tags
https://github.com/WordPress/wordpress-develop/commit/404f397b4012fd9d382e55bf7d206c1317f01148 Patch Third Party Advisory
https://github.com/WordPress/wordpress-develop/security/advisories/GHSA-87h4-phjv-rm6p Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00000.html Mailing List Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/09/msg00011.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/773N2ZV7QEMBGKH6FBKI6Q5S3YJMW357/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ODNHXVJS25YVWYQHOCICXTLIN5UYJFDN/
https://wordpress.org/news/2020/06/wordpress-5-4-2-security-and-maintenance-release/ Vendor Advisory
https://www.debian.org/security/2020/dsa-4709 Third Party Advisory
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