This indicates an attack attempt to exploit a Privilege Elevation vulnerability in Wordpress Plugin BBPress.
The vulnerability is due to the application's failure to properly sanitize user input while handling a craft HTTP request. A remote attacker can send a crafted request to elevated privileges.
WordPress Plugin BBPress plugin before 2.6.5
Privilege Escalation: Remote attackers can leverage their privileges on vulnerable systems.
Apply the most recent upgrade or patch from the vendor.