Users' VPN authentication credentials are unsafely encrypted in Fortinet FortiClient for Windows 5.6.0 and below versions, FortiClient for Mac OSX 5.6.0 and below versions and FortiClient SSLVPN Client for Linux 4.4.2335 and below versions, due to the use of a static encryption key and weak encryption algorithms.
A privilege escalation in Fortinet FortiClient Windows 5.4.3 and earlier as well as 5.6.0 allows attacker to gain privilege via exploiting the Windows "security alert" dialog thereby popping up when the "VPN before logon" feature is enabled and an untrusted certificate chain.