It’s just an idea. I don’t want to say using the comment is the ultimate system. You could for example add some bytes to one of the images in the zip. This wil make it harder to remove/find where the code is hidden and this will also solve the repack problem.
Good idea about self hosting. I’m also prepared to do some testing with this.
Of course, if a user deletes this comment tag from the zip it will not work but I’m sure 99% of the users here doesn’t know a zip file has a comment field, let alone know how to edit it.
They do now!