Horde IMP before 7.0.1 contains a path traversal vulnerability in lib/Compose.php that allows authenticated attackers to read arbitrary files from the server filesystem by embedding traversal sequences after a CKEditor path prefix in img src URLs. Attackers can bypass the stripos() prefix validation by appending sequences such as traversal segments after the matching prefix, causing file_get_contents() to read sensitive files whose contents are then exfiltrated as MIME parts in outgoing email; unauthenticated exploitation is also achievable via CSRF against an active authenticated session.