Is the setting for the default changing?

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.

You may have ad / mal-ware. Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

It’s very sad, but many of the software down-loaders / installers will trick you into installing not only their program, but other programs as well. You have heard of the fine print in shady contracts, right? Well, some installers you need to look at the itsy bitsy teeny weeny fine print. You are thinking you are giving the installer permission to install the program you want by using the recommended option. But if you use the Manual Option Instead, you discover all kinds of stuff that you do not even know what it is or what it does. From now on, everyone needs to Use The Manual Option to put a stop to this.

The default doesn't change. I don't have any strange/malware search engines getting added, it's mostly just youtube video search. Like I said, the main problem is actually not the other search engines getting added, but what seems to be a consequence of it -> firefox randomly landing me at the search preferences page when i type something into the search dialog and press enter (it never happens when I click the right arrow instead of pressing enter), instead of just searching using the default search engine.

wez_schow said

...what I really want to get rid of is firefox sometimes randomly sending me to the search preferences page when i type something in the search dialog and hit enter (which seems to coincide with having multiple search engines set). Sometimes it even simply randomly uses youtube search when I want to google.

This is a strange thing about the panel that I hope will change: if your mouse pointer is hovered over a different search engine or over "Change Search Settings" when you press Enter, the panel behaves as though you click whatever is below the mouse pointer. This gets me once or twice a day when I'm suddenly staring at Amazon or Bing or another unexpected results page. I know what causes it and how to avoid it, but I'm not always that careful...

As long as the default is not changing, the above may be the problem.

Are you running cleanup software that might be modifying files in the profile folder?

Try to delete the search.json file and possible search-metadata.json and search.sqlite files in the Firefox profile folder to reset the search engines to the default.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Firefox will rebuild the search.json file from the default search engines in the "browser\searchplugins" folder in the Firefox program folder and the searchplugins folder in the Firefox profile folder.