CVE-2018-20583: Thephpleague Commonmark

Medium severity, CVSS 6.1. EPSS: 1.6% chance of exploitation in the next 30 days.

Cross-site scripting (XSS) vulnerability in the PHP League CommonMark library versions 0.15.6 through 0.18.x before 0.18.1 allows remote attackers to insert unsafe URLs into HTML (even if allow_unsafe_links is false) via a newline character (e.g., writing javascript as javascri%0apt).

Affected products

• Thephpleague Commonmark: from 0.15.6, up to and including 0.18.0

Published 2018-12-30. Last modified 2026-06-17.