A private MailExtension add-on that works in Thunderbird 68.6.0 (Windows) fails in Thunderbird 75.0b2 (Windows).
The add-on adds a button to the toolbar that, when clicked, opens a new tab and loads a template html page into the tab and then executes a script file to populate the template with data. This is the relevant code in background.js:
const tab = await browser.tabs.create({
url: "list.html"
});
browser.tabs.executeScript(tab.id, { file: "populate.js" });
While in Thunderbird 68.6.0 everything works as expected, in Thunderbird 75.0b2 the new tab is created and shows list.html, but no data is loaded into the page. So I assume that populate.js simply doesn’t get executed. Is this a permissions issue? The console shows no error.