Thread:Project:Support desk/Cannot upload files since the update from 1.22.7 to 1.23./reply (32)

Looking at https://git.wikimedia.org/blame/mediawiki%2Fcore.git/HEAD/includes%2Ffilebackend%2FFSFileBackend.php instead (canonical place) you can see that this line and the call to popen was added in May 2012 and has not changed since then, so some other code likely has changed which (now?) calls this function.