PocketMine-MP before 4.0.3 Operator Privilege Escalation via Case Sensitivity

PocketMine-MP before 4.0.3 does not perform case-insensitive matching when removing operator entries from ops.txt. The removeOp function lowercases the supplied name but only removes an exactly matching entry, so an operator name stored with non-lowercase letters cannot be revoked using the deop command, leaving the player as an operator until the entry is removed from ops.txt manually.