https://github.com/thunderbird/developer-docs/blob/master/add-ons/hello-world-add-on/using-content-scripts.md?plain=1#L57 states that
The messageDisplayScripts API requires the messagesModify permission.
There is no information about which permission tabs.executeScript() (part of the example) requires.
The tabs WebExtension API documentation seems to suggest that it required activeTab. Yet, I found that tabs.executeScript() requires messagesModify as well.