I've recently had an issue adding images to posts that I've sourced from Wikipedia. I can upload them without issue when I download them and upload them from my computer but I can not upload them using the "from the web" option. I get the error message:
Failed to upload image; the format is not supported
Seeing as I can upload them from a computer without issue, it's not actually the format so much as it's the URL or the server on one side or the other acting up.
As an example, I have this issue with both of the images on this article about Hank (textile).
I was able to successfully upload the top image after downloading it to use in an answer on Arts & Crafts but could not add it directly from the link.
I know this isn't the first time I've experienced this but I'm not sure if it's all Wikipedia images or just some of them.
It's possibly related to Error messages when uploading an image "from the web" but that one is a FR and it's not specific to Wikipedia so I'm not sure it's the same thing.
If it is Wikipedia blocking the upload for some reason, it'd be good to know if it's intentional as I might consider getting images from elsewhere.