Examine source code of WhatCampaign

{
  "name": "WhatCampaign",
  "description": "swap out Google Analytics parameters with invalid data",
  "manifest_version": 2,
  "version": "1.0.9",
  "homepage_url": "https://home.oniprojekt.ninja",
  "icons": {
    "48": "WhatCampaign-48.png"
  },
  "permissions": [
    "webRequest",
    "tabs",
    "*://*/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*/*utm*"
      ],
      "run_at": "document_start",
      "js": [
        "active_handling.js"
      ]
    },
    {
      "matches": [
        "*://*/*"
      ],
      "run_at": "document_idle",
      "js": [
        "rewrite_links.js"
      ]
    }
  ]
}