Explain this to me; why is UPnP so insecure? UPnP can only be switched on by a random application if that application has access to the LAN. That application is then _already_ running locally on one of the machines on the network. It can _already_ connect to random machines/ports. If that application now wants to exploit a vulnerability on one of the machines connected to the LAN, it can do it directly, no need to configure any port forwarding to let yet something else in.
I haven't yet read any realistic argumentation on why UPnP is dangerous (and I looked!). Mainly just FUD. The only security issue I can see is that _after_ the baddies take over your PC, they can open up ports.