Thread:Project:Support desk/Cannot upload files since the update from 1.22.7 to 1.23./reply (22)

The solution for safe_mode = On is to set safe_mode to Off. ;-)

Safe mode was a bad idea, also the PHP developers themselves noticed that and recommend to disable it. Safe mode is deprecated since PHP 5.3 and has finally been removed in 5.4. You should not rely on it. MediaWiki is not made to work with safe_mode = On. If you get it working somehow, be happy, but you should not expect MediaWiki to be changed in a way so that things, which are now broken because of safe_mde being On, will start working in the future. That won't happen.