Command (show history) on configuration router why expose you?

it lists the commands you have entered in the past.

The command history feature provides a record of EXEC commands you have entered. The number of commands that the history buffer will record is determined by the history size line configuration command or the terminal history sizeEXEC command.

 its easy for the past 

The command show the previous configuration on the router. it can be dangerous when outsider get the login details of the router and has the know of how to check  or paly around with routers