Once the username was suppressed (oversighted) by checking the option on special:Block, it is expected that the suppressed username will not be shown on the auto-generated list of username, just like what has been done on Special:Blockedusers and Special:Userlist. However, it is found that the protected userpage title of suppressed username will be shown on Special:ProtectedTitles. The protection to the userpage of suppressed username is needed because the suppression cannot stop the user from creating the page. Please fix this bug by hiding up the protected titles of userpage and usertalk page of suppressed users. Thank you very much.
Note: I don't know whether it is appropriate to report this issue as security issue. Please put it in a right place if it is inappropriate to place here. Thank you.