diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e69de29
diff --git a/canvasblocker.xpi b/canvasblocker.xpi
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index 0000000..939f538
Binary files /dev/null and b/canvasblocker.xpi differ
diff --git a/data/inject.js b/data/inject.js
new file mode 100644
index 0000000..f3fc83d
--- /dev/null
+++ b/data/inject.js
@@ -0,0 +1,12 @@
+var getContext = unsafeWindow.HTMLCanvasElement.prototype.getContext
+
+function block(){
+	unsafeWindow.HTMLCanvasElement.prototype.getContext = null;
+}
+function unblock(){
+	unsafeWindow.HTMLCanvasElement.prototype.getContext = getContext;
+}
+
+self.port.on("block", block);
+self.port.on("unblock", unblock);
+self.port.on("detach", unblock);
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diff --git a/doc/main.md b/doc/main.md
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index 0000000..e69de29
diff --git a/lib/main.js b/lib/main.js
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--- /dev/null
+++ b/lib/main.js
@@ -0,0 +1,54 @@
+var self = require("sdk/self");
+var pageMod = require("sdk/page-mod");
+var preferences = require("sdk/simple-prefs");
+var prefs = preferences.prefs;
+var {URL} = require("sdk/url");
+var workers = [];
+var whiteList;
+updateWhiteList();
+
+function updateWhiteList(){
+	whiteList = prefs.whiteList.split(",").map(function(entry){
+		return new RegExp("(?:^|\\.)" + entry.replace(/([\\\+\*\?\[\^\]\$\(\)\{\}\=\!\|\.])/g, "\\$1") + "\\.?$", "i");
+	});
+}
+
+function detachWorker(worker, workerArray) {
+	var index = workerArray.indexOf(worker);
+	if (index != -1){
+		workerArray.splice(index, 1);
+	}
+}
+function checkWorker(worker){
+	var url = new URL(worker.url);
+	if (prefs.blockAll || !whiteList.some(function(entry){
+		return url.hostname.match(entry);
+	})){
+		worker.port.emit("block");
+	}
+	else {
+		worker.port.emit("unblock");
+	}
+}
+
+preferences.on("whiteList", function(){
+	updateWhiteList();
+	workers.forEach(checkWorker);
+});
+preferences.on("blockAll", function(){
+	workers.forEach(checkWorker);
+});
+
+pageMod.PageMod({
+	include: "*",
+	contentScriptWhen: "start",
+	contentScriptFile: self.data.url("inject.js"),
+	onAttach: function(worker){
+		checkWorker(worker);
+		
+		workers.push(worker);
+		worker.on("detach", function(){
+			detachWorker(this, workers);
+		});
+	},
+});
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diff --git a/package.json b/package.json
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--- /dev/null
+++ b/package.json
@@ -0,0 +1,26 @@
+{
+	"name": "canvasblocker",
+	"title": "CanvasBlocker",
+	"id": "CanvasBlocker@kkapsner.de",
+	"description": "Blocks the JS-API for modifying <canvas>",
+	"preferences": [
+		{
+			"name": "whiteList",
+			"title": "White list",
+			"description": "Domains where the <canvas>-API should not be blocked. To add multiple domains seperate them by comma.",
+			"type": "string",
+			"value": "kkapsner.de"
+		},
+		{
+			"name": "blockAll",
+			"title": "Block everything",
+			"description": "If you want to block everything (ignore the white list).",
+			"type": "bool",
+			"value": false
+		}
+	],
+	"author": "Korbinian Kapsner",
+	"license": "MPL 2.0",
+	"version": "0.1",
+	"permissions": {"private-browsing": true}
+}
diff --git a/test/test-main.js b/test/test-main.js
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index 0000000..147f98a
--- /dev/null
+++ b/test/test-main.js
@@ -0,0 +1,12 @@
+var main = require("./main");
+
+exports["test main"] = function(assert) {
+  assert.pass("Unit test running!");
+};
+
+exports["test main async"] = function(assert, done) {
+  assert.pass("async Unit test running!");
+  done();
+};
+
+require("sdk/test").run(exports);