Alloin is right though. It was totally bug, and no bad choice or bad security needed for it to work, only a lack of knowledge of said bug. A player being able to log into a base without even breaking in or being allowed in etc, logging in on claimed land their character had never even been on before? SUPER BUGGY! serious bug!
It would be cool if we had some sort of proper trojan horse mechanic properly implemented but this is certainly not such a thing.