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My girlfriend plays a game that blocks you from naming characters inappropriately, but for some reason it blocks a ton of normal names like "Valerie" or "Fiona" or "Hailey" or "Squidward" or "Sean" so she asked me to look at the game's code to find out why… 🧵

The game has a list of illegal terms separated by a | symbol, something like "lexi|qixils" to prevent a name from having "lexi" or "qixils" anywhere in it. It looked like a fairly standard list of slurs at first until I got to the end of the list…

For some inexplicable reason, the very last blocked term is actually a RegEx filter. I won't bore with the specifics, but an example filter would be "L(A|E|U)X" which means "L, followed by an A or E or U, then X". You might see where this is going…

The issue is that the RegEx tries to use the | symbol, except that's exactly the same symbol that the game already uses to break apart the whole list of filters! This means the 1 RegEx filter actually becomes 3: "L(A", "E", and "U)X"… This 2nd filter then blocks any name with an "E" in it! 💀

Bonus fact: the game doesn't even support RegEx here! Instead it uses an algorithm where it iterates over every possible subsection of the name to see if it matches a banned term which is highly inefficient!