phpbb has many security issues, and always has. If you are looking for a decent, fairly secure bb, I would suggest Simple Machines. I have used them all at one point or another and after all was said and done, I coughed out the cash for vbulletin. The customer support is bar none, it is easy to mod, and there really isnt a more secure bb out there.
Ehfipimp #273 ( Eheim Classic: 2260, 2217, Eheim Ecco: 2236, 2232 ) Fluval FX5