{"id":"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.","aliases":["GHSA-3527-qv2q-pfvx"],"modified":"2026-09-16T11:46:44.803135211Z","published":"2025-05-05T19:52:59.521Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/46xxx/CVE-2025-46734.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-79"]},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/thephpleague/commonmark","events":[{"introduced":"0"},{"fixed":"6fbb36d44824ed4091adbcf4c7d4a3923cdb3405"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"2.7.0"}],"source":"AFFECTED_FIELD"}}],"versions":["2.6.0","2.5.0","2.4.0","2.3.0","2.2.0","2.1.0","2.0.2","2.0.1","2.0.0","2.0.0-rc2","2.0.0-rc1","2.0.0-beta3","2.0.0-beta2","2.0.0-beta1","0.18.1","0.17.4","0.17.2","0.17.0","0.16.0","0.15.7","0.15.6","0.15.5","0.15.4","0.15.3","0.15.2","0.15.1","0.15.0","0.14.0","0.13.4","0.13.3","0.13.2","0.13.1","0.13.0","0.12.0","0.11.3","0.11.2","0.11.1","0.11.0","0.10.0","0.9.0","0.8.0","0.7.1","0.7.0","0.6.1","0.6.0","0.5.1","0.5.0","0.4.0","0.3.0","0.2.1","0.2.0","0.1.2","0.1.1","0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-46734.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"}]}