Bancor Whitehat Hack
In June of 2020 the Bancor team got notified of a major vulnerability in their system. This vulnerability would allow malicious actors to drain approved funds directly out of users' wallets.
The Bancor team set up a rescue mission to exploit their own contracts before any malicious actors had the chance to do so. In the process they managed to save over $400k of user funds. But in the middle of the rescue mission, an automated front-running bot joined in on the action and managed to steal just over $100k of user funds.