Detect real file content for the mimes validation rule - #324
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Why
ValidationRules::validateFile()'s mimes case only compared the client-supplied filename's extension against the allowed list:$file['name'] is fully attacker-controlled — renaming
shell.phptoshell.pdfdefeats this check entirely, sosanitize(['file' => 'mimes:pdf,doc'])would accept a PHP payload as long as it was named with an allowed extension.What changed
mimes now detects the file's real content type via
symfony/mime'sMimeTypes::guessMimeType()(backed by the fileinfo extension) and checks it against the MIME types normally associated with each allowed extension.