{"id":"CVE-2025-46734","aliases":["GHSA-3527-qv2q-pfvx"],"url":"https://o3.security/vulnerability/CVE-2025-46734","summary":"league/commonmark Cross-site Scripting vulnerability in Attributes extension","details":"league/commonmark is a PHP Markdown parser. A cross-site scripting (XSS) vulnerability in the Attributes extension of the league/commonmark library (versions 1.5.0 through 2.6.x) allows remote attackers to insert malicious JavaScript calls into HTML. The league/commonmark library provides configuration options such as `html_input: 'strip'` and `allow_unsafe_links: false` to mitigate cross-site scripting (XSS) attacks by stripping raw HTML and disallowing unsafe links. However, when the Attributes Extension is enabled, it introduces a way for users to inject arbitrary HTML attributes into elements via Markdown syntax using curly braces. Version 2.7.0 contains three changes to prevent this XSS attack vector: All attributes starting with `on` are considered unsafe and blocked by default; support for an explicit allowlist of allowed HTML attributes; and manually-added `href` and `src` attributes now respect the existing `allow_unsafe_links` configuration option. If upgrading is not feasible, please consider disabling the `AttributesExtension` for untrusted users and/or filtering the rendered HTML through a library like HTMLPurifier.","published":"2025-05-05T19:52:59.521Z","modified":"2026-08-12T03:51:35.912755362Z","cvss":{"score":6.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"},"epss":{"score":0.00362,"percentile":0.29823,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"league/commonmark","fixedVersion":"2.7.0"}],"fix":{"url":"https://github.com/thephpleague/commonmark/commit/f0d626cf05ad3e99e6db26ebcb9091b6cd1cd89b","label":"thephpleague/commonmark@f0d626c"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/46xxx/CVE-2025-46734.json"},{"type":"ADVISORY","url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-3527-qv2q-pfvx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-46734"},{"type":"FIX","url":"https://github.com/thephpleague/commonmark/commit/f0d626cf05ad3e99e6db26ebcb9091b6cd1cd89b"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:35.912755362Z"}}