The "{{erasespamedcomments}}" wiki action ("actions/EraseSpamedCommentsAction.php") accepts a "suppr[]" array from "POST" and deletes every wiki page whose tag appears in that array, with no authorization check anywhere in the action body or in the page-deletion path it invokes. Combined with YesWiki's allow-by-default action ACL model, any user who has page write access, which is the default for everyone ("default_write_acl='*'") on a fresh install can permanently delete arbitrary wiki pages, including the front page, admin pages, and pages owned by other users. The action's "delete()" callee is "PageManager::deleteOrphaned()", which despite its name does not check whether the target page is orphaned: it issues an unconditional "DELETE" against "pages", "links", "acls", "triples", "referrers", and "tags" tables.