Steps to reproduce: 1. Set media.autoplay.enabled to false (to take video playback out of the equation) 2. Navigate to http://www.cnn.com/2017/11/06/politics/manafort-bail-mueller/index.html 2. Wait until page is finished loading Actual results: Page continues to take up 70% or more CPU on a Macbook Pro 2015. No user activity is required. Expected results: Minimal CPU use, fans should not kick in. Performance profile: https://perfht.ml/2zmorkE I'm running the latest Nightly on macOS.
I have received two more reports of this from friends using Firefox 57/58 on OS X. One reports, "if you open http://cnn.com , FirefoxCP Web Content shoots up to 40-60% and stays hovering there. Firefox is a constant 5-10%. Chrome and Safari don't do this". This is on OSX 10.12.3 with no add-ons installed. Another reports "CNN causes CPU to spike above 50%" and provided the attached screenshot. This second reporter has the following add-ons: - 1Password Beta - Evernote Web Clipper - Ghostery (set to track, but not block Ads) I've tried to reproduce this but on a MacBook Pro with OSX 10.12.4 I get: Firefox 57: 9.1%~10.6% (for the FirefoxCP Web Content entry) Safari 10.1: 10.2% ~ 13% (for the cnn.com entry) Chrome 62: ~5%
Sorry, my follow up comment refers to cnn.com in general and not the specific article mentioned in comment 0.
Screenshot provided by @birtles is from a Mid-2013 Macbook Air running OSX 10.13.1 (17B48).
I can also confirm that I see the same behaviour on http://thenewdaily.com.au/sport/football/2017/03/10/trump-travel-ban/
Created attachment 8929941 [details] Activity Monitor (All Processes) showing FF CPU usage exceeding 30 percent.png