[Environment:] Browser / Version: Firefox Nightly 63.0a1 (2018-08-20) Operating System: Windows 10 Pro [Prerequisites:] 1. Tracking Protection Basic enabled. [Steps to Reproduce:] 1. Navigate to https://www.kayako.com 2. Scroll down the page and open the messenger. 3. Observe “Kayako” user image. [Expected Behavior:] The image is displayed. [Actual Behavior:] The image is broken.

Added screenshot with broken images in messenger.

The issue is related to `images` breakage. Looking at the devtools console, here are the blocked resources: The resource at “https://www.googletagmanager.com/gtm.js?id=GTM-59T5TN” was blocked because tracking protection is enabled. The resource at “https://pbs.twimg.com/profile_images/1010245395471974400/bA064Oli_normal.jpg” was blocked because tracking protection is enabled. So below are the domains to test: - www.googletagmanager.com - pbs.twimg.com I opened the URL in a fresh browser profile (Firefox Nightly 63, uMatrix installed, normal mode) and the messenger did not load. I disabled the Spoof Referrer option in uMatrix and then WHITELISTED: - support.kayako.com and the messenger chat was triggered but with the broken user images. I whitelisted than: - twimg.com (with all related domains pbs.twimg.com) and the user images were displayed. The other resource (www.googletagmanager.com) didn't help. So in conclusion: - twimg.com is in Disconnect category = [tp-social]

Added uMatrix results.