Thread:Project:Support desk/Cannot upload files since the update from 1.22.7 to 1.23./reply (31)

Yeah, that's totally right, look here: https://github.com/wikimedia/mediawiki-core/blob/REL1_23/includes/filebackend/FSFileBackend.php#L702

This line has changed somewhere between release of 1.22.7 and 1.23 and now uses popen :)