Not exactly a glitch.
You'd have to press the undo button and re-approve the image and do it manually thirteen times.
A while ago, a user programmed a fairly simple script to perform the task,
bro got thousands of approvals in a day just to climb the mods list.
MSmg removed their mod, and disallowed the practice. But it's not really an offence that the Imgflip ToS cover.