Removing redirect link malware
I'd like to get more information to help. Could you show the MIUI version of your phone? See it in Settings -> About Phone -> MIUI version. If you can use adb in your PC? I think It will be helpful if you can show the output of PC command "adb shell pm list packages" and the output of "adb shell ls -l /system/app /system/priv-app"

By the way, if a factory reset can not resolve the problem you can try a full ota update which will reformat the system partition. To do full ota update: Click the Updater app, and then click the menu button in the right top, then click the "Download update" item. !Remember to backup your files!