Froxlor has privilege escalation in SSH key synchronization via symlinked `authorized_keys` path

Froxlor is open source server administration software. Version 2.3.6 contains a symlink-following flaw in the root-owned SSH key synchronization path used for customer FTP users. The provisioning code appends public keys to `~/.ssh/authorized_keys` under a customer-controlled home directory without verifying that the target path is not a symbolic link. If an attacker controls a shell-enabled customer account and can modify files inside the assigned home directory, the attacker can replace `~/.ssh/authorized_keys` with a symlink to `/root/.ssh/authorized_keys`. When Froxlor's privileged cron task later synchronizes SSH keys, it appends the attacker-supplied key into root's authorized key file, resulting in root SSH access. Version 2.3.7 contains a patch.