leave it alone. It's not yours so it's not for you to throw away. If it gets that bad complain to management or if you have it, facilities, and they should intervene, maybe sending out a mass e-mail.
Management do this regularly and nothing gets thrown away by the original owners. Facilities likewise (though maybe once a year they direct the cleaners to do it). When the fridge stinks because it's got 10+ out of date pints of milk in it, it's not useable by anyone.
If I found a used takeaway packet sitting in the corridor, or mouldy food on the countertop in the communal kitchen, I'd throw it away. Those are also rubbish, and are a health hazard, and are obstructing other people's use of the space. I don't see how the fridge is any different.