Horde IMP 4.3.6 and earlier does not request that the web browser avoid DNS prefetching of domain names contained in e-mail messages, which makes it easier for remote attackers to determine the network location of the webmail user by logging DNS requests.

Horde IMP 4.0.4 and earlier does not sanitize strings containing UTF16 null characters, which allows remote attackers to conduct cross-site scripting (XSS) attacks via UTF16 encoded attachments and strings that will be executed when viewed using Internet Explorer, which ignores the characters.

Cross-site scripting (XSS) vulnerability in horde/imp/search.php in Horde IMP H3 before 4.1.3 allows remote attackers to include arbitrary web script or HTML via multiple unspecified vectors related to folder names, as injected into the vfolderlabel form field in the IMP search screen.

Cross-site scripting (XSS) vulnerability in fetchmailprefs.php in Horde IMP before 4.3.8, and Horde Groupware Webmail Edition before 1.2.7, allows remote attackers to inject arbitrary web script or HTML via the fmid parameter in a fetchmailprefssave action, related to the Fetchmail configuration.