Hello,
 Recently I've been seeing several TV show torrents coming down that have standard filenames, but they have .exe as the extension instead of the expected .mkv extension.  How do you block torrents like that?  Thanks for any and all help with this!

Look here: Settings > Transfers > Files
Look for the item that says "Auto-select files in new transfers", select and press the configure button. Now configure it how you want.

Also look here: https://support.tixati.com/file%20auto%20select