However I've heard that some malicious adware manipulates this dialogue, but this seems to be quite rare. I think the best way would be to change to firefox, since the opt-in feature is relatively foolproof (this window appears every time a external application installed an addon and if the user doesn't opt in the addon gets deleted): You could also use Ninite to install and update some of the most popular freeware and open-source software adware-free.

It also protects the start page from being changed.

You could use Spybot: Search & Destroy, which has a browser protection feature. Some education about the risks of her behavior might be more effective than disabling extensions in Chrome. If you configured a child organizational unit. Under Installation policy, choose Force install or Force install + pin. Your sister has probably more to worry about if she blindly installs adware/malware. Go to the app or extension that you want to automatically install. It might be more flexible, but I can imagine that malware developers would modify these policies themselves. You could also try to set up an administrative policy to disable extensions (see documentation). To override the homepage, you could append the -homepage= flag: chrome.exe -disable-extensions -homepage= via the properties of the shortcut icon): chrome.exe -disable-extensions

You can prevent Chrome from loading existing extensions, or installing new extensions by appending the -disable-extensions flag to the command that launches Chrome (e.g.

Chrome installing addons by itself