"Authentication information" here means one thing: a token the add-on generates on your own device for your Keepa account, so the chart loads your settings and tracked products. It is not your Amazon login, not your Firefox account, and not a password. The add-on never sees any of those.

It replaced the previous label, "personally identifying information" - the list got shorter, not longer. No permissions were added. Access is unchanged: keepa.com and Amazon product pages only.

Firefox 140 introduced these labels; the code behind them is the same as it was. Full source goes to Mozilla every release and their reviewers rebuild it to verify.