When the suPHP_PHPPath was set, mod_suphp would use the specified PHP
executable to pretty-print PHP source files (MIME type
x-httpd-php-source or application/x-httpd-php-source).
However, it would not sanitize the environment. Thus a user that was
allowed to use the SetEnv directive in a .htaccess file (AllowOverride
FileInfo) could make PHP load a malicious configuration file (e.g.
loading malicious extensions).
As the PHP process for highlighting the source file was run with the
privileges of the user Apache HTTPd was running as, a local attacker
could probably execute arbitrary code with the privileges of this user.