XWiki Platform Old Core vulnerable to Authentication Bypass Using the Login Action

XWiki Platform Old Core is a core package for XWiki Platform, a generic wiki platform. Prior to versions 14.2 and 13.10.4, all rights checks that would normally prevent a user from viewing a document on a wiki can be bypassed using the login action and directly specified templates. This exposes title, content and comments of any document and properties of objects, though class and property name must be known. This is also exploitable on private wikis. This has been patched in versions 14.2 and 13.10.4 by properly checking view rights before loading documents and disallowing non-default templates in the login, registration and skin action. As a workaround, it would be possible to protect all templates individually by adding code to check access rights first.