I had disabled our custom emojis due to the recent exploit but now that we've upgraded to 0.18.2, these should all be fixed. So I've reuploaded them.
Also reminder that if you've bought us a grog on Ko-fi, you can request to add a custom emoji for yourself added, as a little bonus. 
Ah that's not an exploit really,nor something that removing custom emojis would stop. It's not a massive issue anyway and I'm sure these kind of stuff will be sorted out soon as development has accelerated a lot lately