Simon Cowell — TOILET PAPER ATTACK … On Bev Hills Mansion

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It”s Simon Cowell“s 54th bday today … and he”s marking the occasion by cleaning the TOILET PAPER off his Beverly Hills mansion.

So, who would have the balls to TP Simon”s pad How “bout a group of 5 girls.

Sources tell our sources … the culprits are the ladies from Fifth Harmony, the girl band Simon signed to a record deal after they performed on “X Factor” last season.

Besides the ass paper, the gals also hung a banner that reads, “Happy 87th birthday, Simon!”

With friends like these …