Recently updated addons open their own page when I start Firefox
Every time I update an addon to a new version I get a page telling me I've successfully updated that particular addon whenever I start Firefox. It's is very irritating. The pages don't appear in the Tools/Options/General/Home page box but they open every time I start the browser. I already have a page for Colorful Tabs and another for Webmail Notifier and I can't disable them unless I disable the addons. However, I don't think this is an addon problem, but a Firefox one.
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Some addons load their own page immediately after an update of that extension - once - to explain what the update is all about, such as new or improved features. If that page is being displayed more than once, something is wrong in Firefox prefs.
If you don't want those pages displayed ever, you'll have to check with support for each extension that does that, to see how that "first run" page can be turned off for each each extension. I am not aware of a "standard" pref that covers every extension that does it, and I don't either of the two extensions installed that you mentioned to be able to look for a pref like that.