Paranoiacs will start with "do we need to handle any user messages at all? that's untrusted data!", much less "do we need to support ALL SORTS of image formats, including some handled by obscure, obsolete libraries that noone truly knows how they work?".
The fact that the messaging application allowed untrusted data to escape the sandbox via obscure data processing libraries they didn't write themselves is a proof of lack of internal software risk assessment process. I hope they learned their lesson and code is now reviewed by people not incentivised to rubber stamp everything the moment in lands on their desks.