CVE-2020-4070: w3c Css Validator

Medium severity, CVSS 5.4. EPSS: 0.6% chance of exploitation in the next 30 days.

In CSS Validator less than or equal to commit 54d68a1, there is a cross-site scripting vulnerability in handling URIs. A user would have to click on a specifically crafted validator link to trigger it. This has been patched in commit e5c09a9.

Affected products

• w3c Css Validator: up to and including 2020-01-19

Published 2020-06-22. Last modified 2026-06-17.