Copy and pasting images using the browser's "Copy Image" option does not upload an attachment to the wiki but adds an external URL image

Vincent Massol nope, it's not a duplicate. This issue would be fixed if issue XWIKI-19961 would be fixed (probably).
The main difference is that this issue is about using a specific copy function that only puts the image content in the clipboard and then pasting in the CKEditor while XWIKI-19961 is about copying an actual mixed HTML content, that contains both text and images.

Technically, for XWIKI-19961, the content of the images is not actually in the clipboard, so the editor would need to fetch it from the srcs of the images, while for this issue, using the "copy image" function of the browser, the content of the image is in the clipboard, we just fail to use it (and we use the HTML instead, which is also in the clipboard).

Thus, the functional difference is that this issue is a lot less explicable than XWIKI-19961, and technically this issue should be much easier to fix (XWIKI-19961 requires content to be fetched from the internet, while this one does not).