how about you stop resetting the search engine to yahoo on updates?
Sometimes where there's a Firefox update, the search defaults get set back to yahoo. I have deleted them out, so it's not a matter of they just got reset, and it's not a malware issue. It happens on every computer running Firefox after some updates. Linux machines as well as Windows.
Opaite Mbohovái (2)
There is a bug in Firefox 35 where some users who were updated to Firefox 34 and had their search set as google lost that preference in the update to 35. We are aware of it and have taken steps to make sure it doesn't happen again in future update.
Separate Issue; Update your Flash Player v16.0.0.257 https://www.adobe.com/products/flashplayer/distribution3.html
Bookmark and use this; Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.
Settings Guard for Firefox {web link} Detects and resets changes to settings that are frequently done by add-ons and application installers.