Not able to upload csv file anymore

Hello,

My wordpress site was updated 2 days ago to WordPress 3.9.15
Since then I’m not able anymore to upload csv files ont it (which I really need).
I have this message : “Désolé, ce type de fichier n’est pas autorisé pour des raisons de sécurité.” which means “Sorry, this kind of files is not authorised for security reasons.”
Any help would be greatly appreciated !

Thanks !