The full policy is at https://writermargins.com/privacy/.

This add-on runs in your own browser. It requests your KDP reports from KDP Reports using your own signed-in session and sends us only: the report files and page-read figures, your book list from KDP Reports (titles, author names, ASINs, ISBNs and formats), the date your KDP account started, and whether syncing is working (with the add-on's version). It never reads or sends your Amazon password, cookies or session, reads no other website and nothing else you browse, and does not keep your reports in the browser. Amazon Ads connects separately on writermargins.com through Amazon's own sign-in; the add-on never touches it. We use this data only to show you your sales, ad spend and profit, never sell it, and delete it when you delete your account. Writer Margins is operated by Steppr Limited (company 14433954, England and Wales). Questions: support@writermargins.com.