Firefox users who run add-ons that are not monitored by Mozilla may notice a new notification in Firefox when they visit certain sites. The notification informs them that "some extensions are not allowed" and were blocked from running on that site.
Mozilla writes on a support page: "As of Firefox version 115, we have introduced a new back-end feature to only allow some extensions monitored by Mozilla to run on specific websites for various reasons, including security concerns".
Mozilla makes no mention of the scope of this and the support article is extremely vague. The change is called
Quarantined Domains by Mozilla.