Remember, "Poor writing, not specialized concepts, drives processing difficulty in legal language."*

You see that here. Mozilla chose to use legalese and not plain language, despite there being a movement afoot to try to push (and in some cases legally require) for plain language in legal documents. This one isn't so bad, since they mostly avoid passive voice and don't needlessly capitalize much. Maybe the low frequency jargon is necessary but look at those center embeddings...

  - you upload or input information through Firefox with your use of Firefox
  - When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license with your use of Firefox
  - When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information with your use of Firefox.
  - When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information to help you navigate, experience, and interact with online content with your use of Firefox.
  - When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information to help you navigate, experience, and interact with online content as you indicate with your use of Firefox.

Break it into multiple sentences.

First sentence establishes you input data into firefox when you use firefox (obviously, but maybe not to everyone!). Second clause establishes that when you input that data you give firefox a license to that data which you otherwise own (this could be more clear in a separate sentence). Third clause establishes that the license is to use the information (not to sell it). Fourth clause establishes that they will use it to help you navigate, experience and interact with online content. Fifth clause (as you indicate) establishes that it is your use of firefox that indicates your intention and how they should use your input to help you. As five separate sentences they could make it seem much more reasonable. The embeddings are instead ineffective because they aren't referring to a common category but instead modify an aspect of the former clause.

* https://www.sciencedirect.com/science/article/pii/S001002772...