Bewertet mit 2 von 5 Sternen

Watch out ! New Version 2.1.3 wants full access to Thunderbird and your computer. No explanation given by developer.
Functionality is ok, but requested access not!!

Diese Bewertung wurde für eine vorherige Version des Add-ons (1.8.14.17) abgegeben. 

The legacy add-on (v1.8.14.17) implicitly has full access and there are no indications or warnings about it. It does the same thing as v2.1.3. What are your thoughts on that?

Thunderbird Web Extension needs to specify the permissions to use. There are no major changes from the legacy add-on, even if it's a feature you originally used and you're using permissions.

As you may not have seen, the permissions required by this add-on are:
"MessagesRead", "storage", "accountsRead", "downloads"
・ See your mail accounts and their folders
・ (The wording about "storage" is unknown)
・ Read your email messages and mark or tag them
・ Download files and read and modify the browser ’s download history

It seems that it is Thunderbird's job to warn you beyond the required permissions.
Perhaps this is the case?
https://www.thunderbird-mail.de/forum/thread/85009-add-on-update-verlangt-erweiterte-berechtigungen/

If you are worried, it is one way to stop using it. This add-on is not an important feature addition. But what is clear is that you haven't done anything to worry about.