Mozilla has launched a new method for identifying browser installations. Assemblies distributed from the official website, delivered in the form of exe files for the Windows platform, are supplied with dltoken identifiers, unique for each download. Accordingly, several sequential downloads of the installation archive for the same platform result in downloading files with different checksums, since the identifiers are added directly to the downloaded file.
The effect only appears when loading exe files from the Windows environment. When you try to download from a browser or from the command line in Linux, the exe files are always the same. Archives in non-executable formats are also not modified. It is stated that you can disable dltoken accounting by turning off telemetry in the browser, but it is not clear how managing telemetry in Firefox will help during the first installation and can affect the substitution of data on the server carried out while downloading files from the site (the problem also appears when downloading from Google Chrome). As a workaround to obtain Firefox installation files without IDs, you can initiate a download directly from ftp.mozilla.org.
The reason cited for embedding the dltoken is to associate first-time installs, existing telemetry, and Google Analytics IDs with actual browser downloads. In particular, you can evaluate the reasons for deviations in the number of downloads and installations, and understand which installations are caused by which downloads (for example, you can find out that one downloaded file was used to install several instances of the browser, which explains why too many installations were recorded in a day , not corresponding to the number of downloads).
Source: opennet.ru