So, it looks like Gentoo's unusual use of the games group has lead to a security hole - if Nethack is installed, anyone can modify the game state data and cause it to run arbitrary code. To be honest, I suspected something like this might happen sooner or later - protecting Nethack from this kind of attack probably wasn't seen as important, since if it's installed in the normal way you can't do this (at least, not as easily). Why exactly did Gentoo use the games group in this way, anyway?
Please help.
I didn't find the right solution from the internet.