That is indeed a bummer. Was an extension crammed into your Chrome install (is there anything you don't recognize in chrome://extensions/)?

If you downloaded from SourceForge, it seems you were hit by this: https://httpshaming.tumblr.com/post/95068402386/filezilla-sourceforge-installer-insecure. Meh.

the update come from the app itself :(
no added extensions 

i suspected it modified the skeleton and iterated all profiles settings DB.

it not only changed Search Engine, it also set starting page.

doing something like this should NOT be allowed by Chrome 

is there to your best knowledge an easy way to revert these changes ?

FYI, we do have some protections in place to try and prevent these kinds of things, but at the end of the day if another binary program is running at the same privilege level on the OS as chrome, there's only a limited amount of things we can do if the OS lets it write chrome's configuration files, modify the chrome binary, etc. 

Anyhow, sounds like this isn't an extensions issue. 

re #5, it depends on how aggressive the extra software that Filezilla installed is at modifying your settings. 

You can try opening Chrome settings and clicking the "Reset settings" button. It's way at the bottom, click the "Show advanced settings..." link, then scroll down some more.

As a shortcut, you can type chrome://settings/resetProfileSettings in the address bar, that gets you to the same place.

If that doesn't work, you may want to try running a commercial AV product first, then resetting again.

@Robert
reset settings would still be done per profile.
i have a dozen of them to go over
and would not fix the skeleton profile. everytime i now create a new profile, it sets yahoo :(

Removing Chrome OS, I believe it is not affected by this issue.

Archiving this for now, hopefully tldr was able to clean up the unwanted software that got installed, there's no further action we can take here. 

But there is something you can do. 
Provide a user a easy and secure way to edit/clean up the skeleton template for new profiles 

You can find and delete the file on-disk (it's called master_preferences, probably located in C:\Program Files (x86)\Google\Chrome\Application or %LOCALAPPDATA%\Google\Chrome\Application if you installed without admin privileges), though I wouldn't really call that easy. 

Uninstalling / reinstalling Chrome would also work though that's more destructive.

If you have a master_preferences file that has settings that you don't expect (causing your new profiles to start off with wonky defaults) and wouldn't mind sharing, would you be willing to attach it to this bug report (before deleting it / uninstalling)? 

I'm curious as to exactly got written there.

Hi Robert.
I can't seem to find that file on my mac
$ find . -name master_preferences