Here is what they are working on

Mozilla, known for coordinating and integrating the development of the popular Firefox browser, is drawing flak online after it announced that it is working with social media giant Meta (formerly Facebook).
The Mozilla Corporation is a fully-owned subsidiary of Mozilla foundation. Unlike the latter, the former is a taxable, for-profit entity. The Mozilla Foundation has been a harsh critic of Facebook, especially for its attacks on net neutrality.
Martin Thomas, a Dinguished Engineer at Mozilla, made the announcement in a company blog post last Tuesday. According to him, they are working with Meta to develop a privacy-preserving advertising technology called Interoperable Private Attribution (IPA).
What is the Interoperable Private Attribution (IPA) proposal?
Mozilla and Meta are working on a proposal for an IPA system, which aims to enable conversion attribution without infringing on user privacy like cookies do. Conversion attribution is a marketing process of finding out which channel of communication (social media, banner ads etc.) led to a user performing a desired action (buying a product, signing up etc.).
Attribution is crucial to digital advertising as it helps them understand which advertising campaign works, and which doesn’t, allowing them to tailor their campaigns for more effectiveness in the future. It also helps publishers understand how effective the advertising on their platform is. On the flip side, current attribution practices are a major concern for user privacy. The same critical for Meta as a large chunk of it revenue comes from advertisments on and off platform.
The proposed IPA will address privacy concerns with two key security features. First, it will use multi-party computation (MPC) to ensure that no single entity—websites, browsers, or advertisers—can learn about user behaviour. Secure MPC refers to the cryptographic task of creating methods for parties to jointly compute a function while keeping each party’s inputs private from the other.
The second feature is that the IPA will be an aggregated system that will produce results that cannot be linked to individual users. Currently, this is all the publicly available information about the proposed system.Why the collaboration and why now?
Last year, Google had announced plans to phase out third-party cookies on its popular Chrome browser. This announcement meant that slowly but surely, marketers will no longer be able to track the browsing behaviour of their customers across sites.

This development is okay for companies like Google who are first-party collectors of data, receiving a lot of information about users from across their Android mobile operating system and Chrome browser.But it does make things harder for Meta, which relies on advertisers who come to the platform to leverage the huge amount of data it collects on its users.
This new ad attribution system could be Meta’s attempt at creating an attribution system that is useful for the advertisers on its platform while also not trampling on user privacy.
Unlike Facebook, Mozilla has a relatively unblemished reputation when it comes to data privacy. Their Firefox browser has many privacy features baked into it with the option for a host of extensions and plugins that bolster those features even further.