What is CVE-2020-27620?

CVE-2020-27620 is a medium-severity vulnerability in MediaWiki Skin\, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2020-10-22.

How severe is CVE-2020-27620?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in MediaWiki Skin\

CVE-2020-27620

The Cosmos Skin for MediaWiki through 1.35.0 has stored XSS because MediaWiki messages were not being properly escaped. This is related to wfMessage and Html::rawElement, as demonstrated by CosmosSocialProfile::getUserGroups.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2020-10-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.011 (65.1th percentile), scored 2026-10-03.

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 65.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000

Affected products

MediaWiki Skin\ — versions cosmos
MediaWiki Skin\:cosmos

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

phabricator.wikimedia.org/T265440 (Vendor Advisory)
gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/634749 (Vendor Advisory)
gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/634752 (Vendor Advisory)
gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/634751 (Vendor Advisory)

Frequently asked questions

What is CVE-2020-27620?: CVE-2020-27620 is a medium-severity vulnerability in MediaWiki Skin\, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2020-10-22.
How severe is CVE-2020-27620?: Medium severity. CVSS v3 base score is 6.1 out of 10.