Why this SIMPLE mistake earned a $5000 bug bounty from Reddit

Moral of the story — be careful when you refactor code

Summary

Refactoring code is common place, especially as a code base grows, more complexity is added to existing functionality, and new technologies are introduced that improve performance. Refactoring is usually a pain in the ass since you have to make sure everything that was once working still works in the new format. Any mistake can introduce new bugs, and in Reddit’s case, this bug cost them $5000.