There's unattributed borrowing that goes in the other direction. Which doesn't make either case right. Just observing that it's a multi-directional problem.
user4704
You can report sites that steal SE content via the Contact Us link at the bottom I think.
Is creative commons licensing is like US copyright in the sense that owners have an obligation to protect their work or risk forfeiting legal protections?
This source makes it sound like the answer is 'yes':
"If someone uses your work in a way that contradicts the terms of the Creative Commons license you used, the license for that person terminates. Since they no longer have a license to use your work, they’re committing copyright infringement. You can take action against them the same way you would against someone who was infringing a copyrighted work that isn’t licensed under the Creative Commons structure."
"Whether a failure to follow a Creative Commons License is a breach of contract or a copyright infringement depends on the specific facts of the case."