On 23rd February this year Mozilla announced the release of Firefox versions 2.0.0.2 and 1.5.0.10. These were mainly described as security releases and they did indeed contain a number of security related fixes. However they also contained a number of fixes related to ' Crashes with evidence of memory corruption' (See the release notes for details).

 

None of these mentioned CPU hogging; but, I thought, it's worth a try. So I upgraded to version 2.0.0.2 and reinstated the ForecastFox extention that was giving me all the issues previously. Lo and behold the problem seems to be fixed! I've been running Firefox for the last week and all has been normal - no overnight increases in CPU consumption at all.

 

The caveats to this are that since the 2.0.0.2 release the developers of ForecastFox have made two minor releases so it is just possible that one of these fixed the CPU issue. However I'm convinced the issue was in the browser and not the extension. Also I haven't yet tested the CPU usage over time when running Flash as this was also causing the CPU usage to increase dramatically over time. So it's still possible there may be unresolved CPU issues; but to date I'm satisfied the issue is resolved for me.