A correction release of Firefox 96.0.3 is available, as well as a new release of the Firefox 91.5.1 long-term support branch, which fixes a bug that, under certain circumstances, led to the transmission of unnecessary data to the telemetry collection server. The overall share of unwanted data among all event records on telemetry servers is estimated at 0.0013% for the desktop version of Firefox, 0.0005% for the Android version of Firefox, and 0.0057% for Firefox Focus.
Under normal conditions, the browser transmits "search codes" ("search code"), assigned by search service providers and allowing you to understand how many queries the user has sent through a partner search engine. Search codes by themselves do not reveal the content of search queries and do not include any identifiable or unique information. When accessing a search engine, the search code is specified in the URL, and together with the telemetry, search code counters are transmitted, allowing you to understand that the correct code was sent when accessing the search engine and the search engine was not replaced by malware.
The essence of the identified problem is that if the user accidentally edits the part of the URL with the search code, the contents of this changed field will also be sent to the telemetry server. The danger is accidental unintentional changes, for example, if the user mistakenly adds "&client=firefox-bd" from the clipboard to the field "[email protected]β, then the value β[email protected]Β».
Source: opennet.ru