There also used to be an exploit where you could make a file both a valid .jar Java executable and a valid .gif, which back in the days of Java applets would po

There also used to be an exploit where you could make a file both a valid .jar Java executable and a valid .gif, which back in the days of Java applets would potentially let you execute code when someone loaded your image (e.g. if you uploaded it as your profile picture): https://en.wikipedia.org/wiki/Polyglot_%28computing%29#GIFAR_attack https://en.wikipedia.org/wiki/Polyglot_%28computing%29#GIFAR...