FreeCanvasHack

Privacy protection and quiz tools for Canvas LMS. Free, open source, runs entirely in your browser with no remote servers.

Status: Work in Progress — The core Privacy Guard is functional. The AI Answer Engine is partially working and needs further testing. Not all features are verified on live Canvas yet. Use at your own risk and test locally before relying on it.

Features

Privacy Guard

Prevents Canvas from detecting tab-switching, window switching, and loss of focus during quizzes and tests.

• Overrides document.visibilityState to always return "visible"
• Overrides document.hidden to always return false
• Overrides Document.prototype.hasFocus() to always return true
• Intercepts addEventListener on prototypes and document/window instances to silently block registration of tracking events (focus, blur, visibilitychange, mouseleave, pagehide, paste, copy, cut, freeze, resume, and more)
• Intercepts dispatchEvent to block programmatic firing of tracked events
• Runs synchronously at document_start before any page scripts can register listeners

Killswitch

If the Privacy Guard is removed, bypassed, or the page tries to unpatch the overrides, the killswitch immediately replaces the page with a fake Chrome "Aw, Snap! OUT_OF_MEMORY" crash screen. This prevents Canvas from detecting that you were ever unprotected.

Answer Saver

Automatically fetches your previous quiz submission history from your school's Canvas API, identifies your highest-scoring answers for each question, and auto-fills them when you hover over the question.

Supported question types: Multiple choice, True/false, Fill-in-the-blank, Multiple answers, Matching, Numerical, Essay.

Kiosk Spoof

Injects a fake Canvas Kiosk App navigation bar at the top of your tab.

AI Answer Engine

Connects to your own LLM API to answer quiz questions. Supports any OpenAI-compatible endpoint.

Three answer modes:

Mode	Behavior
Hover Hint	Hover over a question to see the AI-highlighted correct answer
Right-Click	Right-click on a question to auto-fill the answer
Keybind Type	Hover over a question and press a key to auto-type the answer

Installation

1. Download or clone this repository
2. Open Chrome and navigate to chrome://extensions/
3. Enable Developer mode (top right toggle)
4. Click Load unpacked and select the canvashack folder
5. The extension icon will appear in your toolbar

Required setting for local test page

If you want to use the included test page (test-page.html):

1. Go to chrome://extensions/
2. Find CanvasHack and click Details
3. Enable "Allow access to file URLs"
4. Reload the extension

Getting an API Key (for AI Answer Engine)

The AI feature requires an API key from an LLM provider. Recommended free option:

OpenRouter (Free Models Available)

1. Go to openrouter.ai
2. Create a free account
3. Go to Keys in your dashboard
4. Click Create Key and copy it (starts with sk-or-)
5. In the CanvasHack popup, paste the key — OpenRouter is auto-detected
6. Select a free model (look for the (Free) label)
7. Click Test Connection to verify

Other supported providers: OpenAI, Google Gemini, Groq, Together AI, Hugging Face, Mistral AI, DeepSeek, Cohere, Cloudflare Workers AI, and local models via Ollama.

AI Setup Steps

1. Click the CanvasHack extension icon to open the popup
2. Click the AI Answer Engine card
3. Paste your API key (provider auto-detected from key format) or select from dropdown
4. Select a model
5. Click Test Connection to verify
6. Choose an answer mode
7. Click Save AI Settings

Testing

A test page is included at test-page.html. Open it via file:// in Chrome to test:

• 10 questions of various types
• Click answers and submit for grading
• Right panel simulates what Canvas would report to a teacher
• Green = BLOCKED (guard working), Red = LEAKED (guard broken)
• Open browser console and run testAutoType() to test auto-type mechanism
• Run testAPI() to test your API connection from the page

Project Structure

canvashack/
  manifest.json      Extension manifest (Manifest V3)
  background.js      Service worker — message handling, API test proxy
  content.js         Content script — injects guard, kiosk bar, feature scripts
  inject.js          MAIN world — overrides visibility/focus, blocks events
  quizanswers.js     MAIN world — auto-fills from Canvas API submissions
  ai-answers.js      MAIN world — AI-powered answer system
  popup.html/js/css  Extension popup dashboard
  test-page.html/js  Local test page mimicking Canvas quiz
  README.md          This file

How files interact

content.js runs in the isolated content script world at document_start. It immediately (synchronously) reads inject.js via XHR and injects it into the MAIN world via script.textContent. This guarantees inject.js runs before any page scripts. Feature scripts (quizanswers.js, ai-answers.js) are injected later as <script src> elements after async settings load.

content.js (isolated, document_start)
  ├─ Phase 1 (sync): inject.js → MAIN world via script.textContent
  └─ Phase 2 (async): quizanswers.js, ai-answers.js → MAIN world via script src

popup.js ↔ background.js (message passing for API test)
popup.js → chrome.storage.local → content.js

Configuration

Settings stored in chrome.storage.local:

Key	Default	Description
answerSaver	true	Fetch and auto-fill previous best answers
privacyGuard	true	Privacy guard on/off
killswitch	true	Crash page if guard is removed
kioskSpoof	false	Show fake kiosk browser bar
aiMode	"off"	Answer mode: off, hover, rightclick, keybind
aiProvider	"openrouter"	Auto-detected LLM provider
aiApiKey	""	Your API key
aiModel	"google/gemma-4-26b-a4b-it:free"	Default model
aiEndpoint	OpenRouter URL	API endpoint
aiKeybind	"y"	Key to trigger auto-type
aiAutoTypeSpeed	50	Milliseconds between characters
blockedUrls	[]	URLs to skip
showInjectedUI	true	Show on-page UI

Privacy

The extension makes zero connections to any external server operated by the extension authors. All features run in your browser:

• Privacy Guard overrides local browser APIs only
• Answer Saver calls your school's Canvas instance only
• Kiosk Spoof is purely local DOM injection
• AI Answers calls only the endpoint you configure
• API keys are stored in chrome.storage.local and never sent anywhere except your chosen endpoint

License

Free and open source.