Originally Posted by kar_bon I've updated the extension ExternalData to the newest version, but this did not eliminated the error. I've inserted into the mime.types file of the MediaWiki source the line Code: application/csv csv there was only an entry with "text/csv csv". I've uploaded a new version of the data file for Proth primes of the form k*b^n+1, least n-values and no error occured. Try again now if the issue is solved for now. I've searched for an error like this, but found no solution, an update to a newer MediaWiki version is not needed (and could also create other issues then).