5 digit number added to upload filename link on rendered page

I just noticed that for some reason, all uploads (pdf, jpg, etc.) filenames have a 5 digit number added to them in the rendered page they’re on. So, a file called “test.pdf” is uploaded, the media file as shown on the media’s page does not have the number. Yet, when the page that has a link to the file is rendered, the characters .98043. are added to the filename before the .pdf. So test.pdf becomes test.98043.pdf. I don’t know if a plugin is adding this, and I’ve never seen it before. I do have the shortpixel plugin to optimize images, but I don’t remember it doing this. I’ll check their forum, but has anyone else seen this?