The PHP Group has retracted
PHP 5.2.7. The security issue in PHP 5.2.7 has dire security implications for phpBB2 installations. For phpBB3 the issue can result in cosmetic problems.
If you have already updated to that version, it is essential that you turn the setting "magic_quotes_gpc" to off in your php.ini file and update, promptly, to PHP 5.2.8 when it becomes available.