While we are here ....
This is related enough to be mentioned here.
When images are copied to Imgur they are not only notionally assigned CC-by-whatever-the-current-flavour-is rights BUT also are subject to Imgur's TOS for unpaid Imgur posts. These are draconian. I raised this issue some years ago and was assured at the time that the Imgur conditions applied to paid Imgur contributions would be applied. However, in 'no time flat' the language used made it clear that committing an image to Imgur storage was (allegedly) waiving your rights to it.
But wait - it's worse ... . So if you LINK to an image because embedding it would result in SE CC-by-xxx ing it, and Imgur making off with it, and if somebody then converts the link to an Imgur stored image, as people'helpfully' do on an ongoing basis, then notionally the helpful editor has assigned CC-by-xxx to your image and given Imgur the right to have their irrevocable way with it without you knowing, let along having been asked what you think.
No?