^^ I was on a 1 year post grad work permit...I was trying to figure out if it was extendible or not as well. I found out that it IS NOT extendible and you can't work on implied status from a PGWP. A lot of people on this website say that it's ok to work if you send in a open work permit, but that is simply false information.
If you continue to work, you put yourself into the hands of CIC and can face some serious consequences. Even if you tell them you didn't know you couldn't work, they won't care...ignorance isn't a sufficient answer to them. Be careful what you choose to do. It sucks having to stop working like I had to, but the other consequences are way worse.