I've been having quite a problem for about a year now (this happens on all versions, 1.3 or 1.4). This isn't too big of a deal, but I would like to find the cause or fix for it regardless.
When a user without permission to a page, forum, or thread tries to visit the page it doesn't work and instead the user gets a white page with scrambled text and symbols on it, instead of the usual "No permission" error that's built into XenForo. This happens on all browsers, and all versions of XenForo which makes me believe that it might possibly be an add-on, but I highly doubt it since it's been an issue for as long as I can remember. The add-ons I use: NodesAsTabs, PostRating, SeparateSticky&Normal, sonnbStopSpamHere, TaigaChat, XenTRWhoHasVisited, XenPorta, TagMe, WidgetFramework
Here's what it looks like:
Again, this only happens when a user visits a page that their user group does not have permission to view, such as a hidden thread or page.