Sometimes, the page_props table may end up containing invalid entries where pp_page is 0. If those invalid entries include the PFDefaultForm prop pointing to some form, PageForms will pick it up and present it as the default form for any page, because getDefaultForm will issue a query with pp_page = 0 when given a nonexistent title,

The issue of the invalid entries is unlikely to be the fault of PageForms given that it does not seem to directly write to page_props itself, but getDefaultForm could be made more robust when working with nonexistent titles.