The ESPN Custom Logos web extension/add-on for Mozilla Firefox and Google Chrome does not store any private data for users. The only data it retrieves are the SWID and espn_s2 cookies which are necessary for extension to authenticate to a fantasy team to save the image as the logo. This replicates the same process that ESPN uses to change custom logos and does not collect anything beyond that process at runtime. It also does not store anything at all, with all code running locally in your browser.