I considered (and was planning on) adding a "block URL" feature - but the issue of how to store those sensitive URLs (to block) came up. Because localStorage and sync storage in Chrome is not sandboxed or encrypted, the blocked list would be "in the open" to other extensions. Yes, you could hash the urls you'd hope to block, but then there would be no way to read that list back to the user at a later point in time, and slight mismatches in URL schemes would lead to an imperfect system. So simply toggling Research Mode and researching pages of interest is the best option, IMO.
I don't cache any personal info in localStorage or sync storage (which at least Chrome does not encrypt :< ). The api results are stored in a local variable within the scope of the extension. And the "history" is a hashed and padded blob.
This is also why I released it for both Chrome and FF, since some people assign different use cases to different browsers. The code is also public/open-source.
I would also like to express my appreciation for making a firefox addon as well. I feel like ff is often left by the wayside.
Unless things have changed from a couple of years ago (highly doubt it), I don't think this is the case. https://groups.google.com/a/chromium.org/d/msg/chromium-exte...
Why couldn't you use chrome.storage.local or the background page's localStorage? Either should protect the data from other extensions and not expose it to third parties.
Firefox provided it: "The simple storage module exports an object called storage that is persistent and scoped to your add-on." https://developer.mozilla.org/en-US/Add-ons/SDK/High-Level_A...
But all Chrome's docs said were the previously mentioned warning about not using it to store confidential user info.
So, to answer your question: caution
Actually, if you go back to my init commit on Github - you can see that I originally used the chrome.storage API. I extricated it from the code - except for the non-sensitive settings
There should be a way to block domains that you don't want searched, otherwise secret URLs such as youtube private links, google docs, etc are exposed. One scary thing is you are potentially exposing them to third parties, by searching reddit, HN, and google.
This is a pretty good example of why people need to be wary of chrome extensions they install. They sit in an advantageous position where violating things like SOP, CSP Rules (depending on the browser) and more is okay by using the background page.