This is a simple exploit I created that can be added to any website to check if a user is using GoGuardian, as well as their associated email address.
Q: Is this exploit harmful?
A: Not really. It doesn't do anything maliciously to the user.
Q: How does it work?
A: When your browser is connected to GoGuardian, an injected popup is displayed on every website informing you that you're connected and being monitored by GoGuardian. Unfortunately, this allows websites to hook into that popup and check whether a user is using GoGuardian. This wouldn't be that much of an issue... if it weren't for the fact that the popup includes your school email address, which can be used maliciously to collect information on what student viewed your website.
Note: I am not responsible for how you choose to use this exploit, nor do I condone using it for malicious intent. This is merely a demonstration on how extension-injected popups can be exploited.