One of the main arguments brought forth for the switching to the WebExtensions system for browser extensions was that it made cross-browser extensions easier. Firefox users may now reap the benefits of this promise, as Mozilla has implemented functionality in the browser to import extensions from other browsers.
The feature, which is in testing at the moment, can be enabled by all users of the latest stable version of Firefox.
The feature is limited at the time to Google Chrome and select extensions. Even though Firefox and Chrome extensions use the same framework, WebExtensions, they are not compatible immediately. Firefox users who attempt to install extensions from Chrome’s Web Store may notice that this is not working.
Seems like it. The article also mentioned that there are only 73 pairs available, so it sounds like Mozilla has to explicitly define what Chrome extensions corresponds to what Firefox extension.