XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. XWiki Platform Legacy Old Core and XWiki Platform Old Core versions 9.8-rc-1 through 16.4.6, 16.5.0-rc-1 through 16.10.4, and 17.0.0-rc-1 through 17.1.0, any user with editing rights can create an XClass with a database list property that references a password property. When adding an object of that XClass, the content of that password property is displayed.

In practice, with a standard rights setup, this means that any user with an account on the wiki can access password hashes of all users, and possibly other password properties (with hashed or plain storage) that are on pages that the user can view. This issue is fixed in versions 16.4.7, 16.10.5 and 17.2.0-rc-1.