Roundcube Webmail before 1.5.12 and 1.6 before 1.6.12 is prone to a information disclosure vulnerability in the HTML style sanitizer.
https://roundcube.net/news/2025/12/13/security-updates-1.6.12-and-1.5.12
https://github.com/roundcube/roundcubemail/commit/08de250fba731b634bed188bbe18d2f6ef3c7571