Enterprise Protection Backslash URL Rewrite Bypass

Enterprise Protection contains a vulnerability in URL rewriting that allows an unauthenticated remote attacker to send an email which bypasses URL protections impacting the integrity of recipient's email. This occurs due to improper filtering of backslashes within URLs and affects all versions of 8.21, 8.20 and 8.18 prior to 8.21.0 patch 5115, 8.20.6 patch 5114 and 8.18.6 patch 5113 respectively.