Rest assured - such rackets ARE SCAMS that can cost you $$$$$$$$$! (You'll find references/prohibitions in the extensive documentation that Upwork provides all members)... Your check will probably clear the bank immediately - your balance will probably reflect such. Then you'll send them (or a 3d party) a few hundred bucks back... and a few days later the counterfeit check will bounce and your bank will take the whole amount out of you account.

You will be screwed... the bank won't refund your $.

But they have nothing to do with Upwork... 'anymore than telemarketing scams have anything to do with your email or phone provider.

You owe it to Upwork, yourself and fellow freelancers to report such suspicious activity REPORT this to Upwork Support ASAP. They devote a boatload of $, technology and manpower to identify and ban such scamming"clients", their IP address, etc. They can't fix a problem unless they know about it.

The relationship that we freelancers share with UW is a 2-way street!