The simplepush server iterates through the application installations and pushes a notification to the server provided by deviceToken. But this is user controlled. If a bogus applications is registered with bad deviceTokens, one can generate endless exceptions when those endpoints can’t be reached or can slow the server down by purposefully wasting it’s time with slow endpoints. Similarly, one can provide whatever HTTP end point they want. This turns the server into a DDOS vector or an anonymizer for the posting of malware and so on.