Well, the reward collecting is going to be a public ceremony I would imagine -- news of your newly-discovered Monero vulnerability will break before you have the chance to plunge your reward money into a highly-leveraged short. So you'll have to borrow funds, which wouldn't be as easy. But you can still use your reward money to capitalize on the fallout -- it would likely take a long time for the price of XMR to completely unwind.
It would honestly be more practical to build something that monitors all Lightning Network transactions to trace where funds are going. But I have some drinking to do, so you guys have at it.
I highly doubt that programmers and coders capable of breaking the code would even be interested in such a move,,, these types of people have a very different motivation and the fame is going to earn them millions down the road with a great job and advisory role;)
But if they did, they would of course involve a friend and third party to do that market manipulation.
Great for us XMR holders because we know it will not be broken. Free advertising;)