Originally published on hexisteme notes .

My blog publisher draws a chart image, pastes the post into a hosted blog editor, and clicks publish on a schedule. The editor does not always keep the image I paste as is. In my probes it re-uploaded some pasted images to Kakao's CDN ( blog.kakaocdn.net ) and rewrote the src , left others at their original URL, and dropped an image that returned 404 from the post without an error. The re-upload is asynchronous. So before the publish click, the publisher checks the editor: the right number of images, in order, rehosted on the CDN, each with the width and height of the PNG I generated.

That last condition was the whole identity check.…