Thomas Reed has been keeping track of MacUpdate adware in his own blog at Malwarebytes. It's well worth reading his article here. You can read about the initial discovery of what's going on at MacUpdate along side Thomas' useful insights:
Has MacUpdate fallen to the adware plague?
Following Mr. Urdaneta’s hints, I sought out the Skype page on the MacUpdate site and downloaded the app. The result was a file named Skype Installer.dmg, which seems legit on first glance. However, opening this disk image file results in a MacUpdate installer,Note that between Thomas and myself, we've found that the MacUpdate adware installer flips between a number of different adware installations. I've witness the attempt to install Yahoo! adware as well as MacBooster.
very similar to the adware-riddled custom installers used by sites like Download.com and Softonic. . . .
The nightmare of the matter is that this installer asks for your ADMINISTRATOR PASSWORD, which means you're giving this malware access to the deepest depths of your Mac home. DON'T DO IT! Anything-at-all could be installed after you've provided that password to the malware.
I have a name I use for people who foist nastiness on potential customers:
The marketing folks who seriously care about the welfare of their collaborators, their customers, are called:
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I'll be adding further observations of the infestation as I find them and consider them helpful and relevant.