Monday, February 19, 2018

Remedying high CPU usage in Firefox when visiting the Esquire site

I recently visted the Esquire site, and Firefox hung for many long minutes, with Process Explorer (a Task Manager alternative) showing very high CPU usage. To stop this, I had to end the Firefox process.

I experienced this with Firefox 38.8 and 39.0.3, both on Windows XP SP3. These two browser versions are relatively close to one another, but in different computers, which led me to conclude, that the issue is server-side.

The culprit is a possibly malformed font file with the .css extension:

assets.hearstapps.com/sites/esquire/assets/css/fonts-deferred.afa78bb.css

This is the file that you have to block.

If you use NoScript already, don't visit the Esquire site yet, and go instead to NoScript Options.
• In the Other tab, there is the ABE subtab;
• Click the USER rule/set in the left pane, and paste the following code into the right pane:

#ESQUIRE HIGH RESOURCE USAGE
Site .assets.hearstapps.com/sites/esquire/assets/css/fonts-deferred*
Deny INCLUSION(FONT,CSS)

#This is a widespread tracker or ad service of some kind.
#Used by Esquire, too.
Site .nexus.ensighten.com
Deny

Click OK.

You can now try out the Esquire website. Works for me.

05.10.2018 Update: I've shortened the Site line to end with fonts-deferred*. NoScript's ABE should still match the pattern. The reason was, that the original file was fonts-deferred.afa78bb.css, which contains alphanumeric content that may be used for version tracking server-side. Removing those numbers and including a wildcard makes the line relatively future-proof from newer versions of the same file.