Neck b

mainfest.json

{
    "name": "MyExtension",
    "version": "1.0",
    "manifest_version": 2,
    "description": "Turn your avatar into a neckbeard",
    "permissions": ["tabs", "http://*/*"],
    "content_scripts": [
        {
          "matches": ["https://twitter.com/*", "https://github.com/*"],
          "js": ["scripts.js"]
        }
    ]
}

scripts.js

if(location.origin === "https://twitter.com") {
    document.getElementsByClassName('DashboardProfileCard-avatarImage')[0].setAttribute('src', 'https://royal-crate.surge.sh/beard.JPG');
} else if(location.origin === "https://github.com") {
    var avatars = document.getElementsByClassName('avatar');
    console.log(avatars);
    for(var i = 0; i < avatars.length; i++) {
            console.log(avatars[i]);
            avatars[i].setAttribute('src', 'https://royal-crate.surge.sh/beard.JPG');
    }
}