Unrar all file in directory without prompting

You need to specify -o+ to enable automatic overwriting:

find . -name "*.rar" -exec unrar x -o+ {} \;

From unrar usage:

o[+|-]        Set the overwrite mode

Do not list *.rar files in other directories (only where the command is run) using maxdepth. Remove print or messages on the screen with -inul.

find . -maxdepth 1 -type f -name "*.rar" -exec unrar x -o+ -inul {} \;