I didn't find Upwork's contract without signing up, but before Elance merged with oDesk to become Upwork they had pretty onerous terms in their services agreement⁰:

9.Indemnification Contractor will defend, indemnify, and hold harmless Client against any damage, cost, loss or expense arising from a claim, suit or proceeding brought against Client (i) alleging that any Work Product infringes upon any Intellectual Property Rights, (ii) alleging that any Work Product misappropriates any trade secrets, of any third party, or (iii) arising from Contractor's breach of the terms of this Agreement.

I read that to mean that if a client I did work for is sued for IP infringement, even if no IP infringement occurs, I need to pay for the client's defense out of my own pocket.

⓪ - https://www.elance.com/p/legal/independent-contractor-servic...