Mozilla will switch the manual review process to an automated process for WebExtension submissions to the official Mozilla Add-ons website (Mozilla AMO).
Developers who submitted a browser add-on for Firefox up until now had to go through a sometimes lengthy review process before their new add-ons or add-on updates would become available on Mozilla AMO.
Mozilla reviewed any add-on manually that developers submitted to the store. This meant better vetting of browser extensions, and a lower risk that malicious or otherwise problematic add-ons would land on Mozilla AMO.
The downside to the review process was that reviews would sometimes take weeks before they were done. Not good from a developer point of view, especially if the release or update was time critical, for instance when it fixed issues that crept up in new versions of Firefox, or fixed major issues in the add-on.
The extra vetting of extensions was a distinct advantage over Chrome's automated processes, the longer review time a distinct disadvantage.
Mozilla enabled a system for Firefox recently that automates the previously manual review process. It does not mean that add-ons won't be reviewed manually anymore though.
Add-ons built on the WebExtensions API will now be automatically reviewed. This means we will publish add-ons shortly after uploading. Human reviewers will look at these pre-approved add-ons, prioritized on various risk factors that are calculated from the add-on’s codebase and other metadata.
The new process checks extensions that get uploaded by developers automatically similar to how extensions are checked for Google Chrome.
Manual reviewers will still review extensions, but they will do so after the extensions are already live on Mozilla AMO. Add-on reviews are prioritized based on risk factors and other data, and add-ons may be pulled from AMO if they fail manual reviews.
Issues that arise during review can still lead to rejection of a version or a whole listing.
In short: Firefox extensions have to pass automatic checks when they are uploaded by their developers. If they do pass those checks, they are made available on Mozilla AMO. Mozilla will review all add-ons just like before, but after the making available on the official site.
The change benefits developers, as it reduces the time between uploading an extension to Mozilla's servers and it becoming available to Firefox users.
The downside is that it increases the chance that extensions may become available that are problematic in one way or the other. Google for instance has to remove malicious or privacy invasive extensions that slipped past the company's automated review process regularly from the Chrome web store.