Latest update breaks Canvas Website and Github Unless user clears _all_ settings

Since the update I can no longer use the Canvas(Educational platform) website. https://vccs.instructure.com/

Description

After update if I do not disable the addon the site will no longer work. It worked until today when the extension autoupdated. Unless the user clears all settings the thing won’t work. So something’s going on here. I’ve included both the original and the modified settings at the bottom.

It prevents someone from using the site and since it’s no supposed to be blocking anything as the icon doesn’t change you can’t even white list the site.

Expected Behavior

It should just work. It worked before the last update.

Current Behavior

The site fails to load. And the following is written the browser console.

Error: WebExtension context not found!  ExtensionParent.jsm:778:13
Error: Attempt to postMessage on disconnected port  frame.js:121:5
Loading failed for the <script> with source “https://www.google-analytics.com/analytics.js”.  vccs.instructure.com:1
ReferenceError: $ is not defined

Possible Solution

I have no idea what I’m doing but maybe this information below might help you out more.

Extra information. If I tell canvas blocker to ask for permission and then block it, it works just fine. Also if I disable the “DOMRect API” it also works just fine. So I don’t know what’s going with this site. If I block access to it, or prompt and then block it works fine but if I try to just fake it, the site will fail with the message Error: Attempt to postMessage on disconnected port showing up. Which I think is from canvas blocker but who knows.

OK after some more digging this is the issue this section of code.

			notificationCounter[data.messageId].count += 1;
			if (!sentAPIs[data.api]){
				sentAPIs[data.api] = true;
				port.postMessage({"canvasBlocker-notify": data});
			}
		}
	}

It is doing something with the Canvas website. When I tell it to just fake out reading on the DomRect API it’ll give me that error and stop the site from loading but if I prompt or block the site it’ll work just fine. As in if I set the mode to “block” no error will pop up.

Steps to Reproduce (for bugs)

1. Try to go to the site. See that it fails to load with the messsages above.
2. Can’t get it work anymore without disabling the thing or setting the mode to prompt or block.
3. Get frustrated and post a bug report here.

Context

I was trying to do my homework for my classes that are online.

Not needed itworked yesterday.

Your Environment

• CanvasBlocker Version used:0.5.11
• Firefox version incl. 32- or 64-bit:64bit
• Operating System and version (desktop or mobile):Desktop
• Installed addons:

Classic Add-ons Archive	2.0.1	true	[e-mail]
Classic Theme Restorer	1.7.7.2	true	ClassicThemeRestorer@ArisT2Noia4dev
Decentraleyes	2.0.11	true	jid1-BoFifL9Vbdl2zQ@jetpack
DownThemAll!	3.0.8	true	{DDC359D1-844A-42a7-9AA1-88A850A938A8}
DownThemAll! AntiContainer	1.5	true	[e-mail]
Link Cleaner	1.5	true	{6d85dea2-0fb4-4de3-9f8c-264bce9a2296}
No Transition	1.1.8	true	{8b5fde66-c64d-4a33-99f1-c7c94138d67e}
NoScript	5.1.8.4	true	{73a6fe31-595d-460b-a920-fcc0f8843232}
Tab Groups	2.1.4	true	tabgroups@quicksaver
uBlock Origin	1.20.0	true	[e-mail]

Your Settings

{
	"logLevel": 1,
	"urlSettings": [],
	"hiddenSettings": {},
	"expandStatus": {},
	"displayHiddenSettings": false,
	"whiteList": "",
	"sessionWhiteList": "",
	"blackList": "",
	"blockMode": "fake",
	"protectedCanvasPart": "readout",
	"minFakeSize": 1,
	"maxFakeSize": 0,
	"rng": "nonPersistent",
	"protectedAPIFeatures": {},
	"useCanvasCache": true,
	"ignoreFrequentColors": 0,
	"minColors": 0,
	"fakeAlphaChannel": false,
	"persistentRndStorage": "",
	"persistentIncognitoRndStorage": "",
	"storePersistentRnd": false,
	"persistentRndClearIntervalValue": 0,
	"persistentRndClearIntervalUnit": "days",
	"lastPersistentRndClearing": 1561344734600,
	"sharePersistentRndBetweenDomains": false,
	"askOnlyOnce": "individual",
	"askDenyMode": "block",
	"showCanvasWhileAsking": true,
	"showNotifications": true,
	"highlightPageAction": "color",
	"highlightBrowserAction": "color",
	"displayBadge": true,
	"storeNotificationData": false,
	"storeImageForInspection": false,
	"ignoreList": "",
	"ignoredAPIs": {},
	"showCallingFile": false,
	"showCompleteCallingStack": false,
	"enableStackList": false,
	"stackList": "",
	"protectAudio": true,
	"audioFakeRate": "100",
	"audioNoiseLevel": "minimal",
	"useAudioCache": true,
	"audioUseFixedIndices": true,
	"audioFixedIndices": "15",
	"historyLengthThreshold": 2,
	"protectWindow": false,
	"protectDOMRect": true,
	"domRectIntegerFactor": 4,
	"blockDataURLs": true,
	"protectNavigator": false,
	"navigatorDetails": {},
	"displayAdvancedSettings": false,
	"displayDescriptions": false,
	"theme": "dark",
	"dontShowOptionsOnUpdate": false,
	"isStillDefault": false,
	"storageVersion": 0.5
}

here’s the reset settings after changing theme to dark.

{
	"logLevel": 1,
	"urlSettings": [],
	"hiddenSettings": {},
	"expandStatus": {},
	"displayHiddenSettings": false,
	"whiteList": "",
	"sessionWhiteList": "",
	"blackList": "",
	"blockMode": "fake",
	"protectedCanvasPart": "readout",
	"minFakeSize": 1,
	"maxFakeSize": 0,
	"rng": "nonPersistent",
	"protectedAPIFeatures": {},
	"useCanvasCache": true,
	"ignoreFrequentColors": 0,
	"minColors": 0,
	"fakeAlphaChannel": false,
	"persistentRndStorage": "",
	"persistentIncognitoRndStorage": "",
	"storePersistentRnd": false,
	"persistentRndClearIntervalValue": 0,
	"persistentRndClearIntervalUnit": "days",
	"lastPersistentRndClearing": 0,
	"sharePersistentRndBetweenDomains": false,
	"askOnlyOnce": "individual",
	"askDenyMode": "block",
	"showCanvasWhileAsking": true,
	"showNotifications": true,
	"highlightPageAction": "none",
	"highlightBrowserAction": "color",
	"displayBadge": true,
	"storeNotificationData": false,
	"storeImageForInspection": false,
	"ignoreList": "",
	"ignoredAPIs": {},
	"showCallingFile": false,
	"showCompleteCallingStack": false,
	"enableStackList": false,
	"stackList": "",
	"protectAudio": true,
	"audioFakeRate": "100",
	"audioNoiseLevel": "minimal",
	"useAudioCache": true,
	"audioUseFixedIndices": true,
	"audioFixedIndices": "11",
	"historyLengthThreshold": 2,
	"protectWindow": false,
	"protectDOMRect": true,
	"domRectIntegerFactor": 4,
	"blockDataURLs": true,
	"protectNavigator": false,
	"navigatorDetails": {},
	"displayAdvancedSettings": false,
	"displayDescriptions": false,
	"theme": "dark",
	"dontShowOptionsOnUpdate": false,
	"isStillDefault": false,
	"storageVersion": 0.5
}

[kkapsner]

https://github.com/kkapsner/CanvasBlocker/releases/tag/0.5.12 is out

[kkapsner]

When the OP also uses Waterfox one issue is enough 😉 Let’s see how I can solve this.

Regarding the support drop of Firefox < 57: I want to support Waterfox as much as I can. Not sure if it’s possible…