Am I liable for copyright infringements made by a non-affiliated source?
<p>Let's say that I find a non-affiliated source that offers some creative work under a copyleft license and I decide to use that work, stating where I found it and under which license. If in the future that 3rd party gets sued for copyright infringement, can I be considered liable?</p>

<p>If you used some creative work of mine without my permission (I'm the copyright holder, and you have no license giving you permission) then I can sue you to make you stop using my work, to get payment for damages, and to get payment for statutory damages. If you used my work because someone else told you wrongly that you had a license, that's very unfortunate for you, but is no reason why I wouldn't or shouldn't sue you.</p>
<p>Obviously in this situation that third party did something badly wrong. I can sue both of you together to make sure that I get payment from whoever has deeper pockets. You can also sue that third party if you think that their lying, or being mistaken, about a non-existing license  caused you damages, or if there is a contract or something that makes them responsible.</p>

copyright