Weakness
In Roundcube Webmail 1.6.x before 1.6.16 and 1.7.x before 1.7.1, the remote image blocking feature can be bypassed via a crafted CSS var() value in an e-mail message, which may lead to information disclosure or access-control bypass.
References
- https://github.com/roundcube/roundcubemail/commit/59cca80908a61e662c5f81741449e9aeb91e8abe
- https://github.com/roundcube/roundcubemail/commit/852350486b88b35b8544e8a630fad89e99e2150a
- https://github.com/roundcube/roundcubemail/releases/tag/1.6.16
- https://github.com/roundcube/roundcubemail/releases/tag/1.7.1
- https://roundcube.net/news/2026/05/24/security-updates-1.6.16-and-1.7.1
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