The OpenWikiPlugin plugin (AKA "OpenWiki") is a NeWikiPlugin that provides a visual indication of the setting of the "Open Wiki" flag, a wiki-wide feature introduced by this plugin, which also provides a means so that other plugins or wiki features can check the state of the flag.
The plugin's isOpenWiki() method provides the ability to incorporate a wiki-level configuration check permitting the restricting of plugin access between pages without resorting to ACL processing. That is, when the wiki property "org.apache.wiki.open-wiki" is set 'true' those plugins that incorporate the feature test can then throw exceptions or produce warning messages rather than grant access to pages.
This is to acknowledge that for many wikis (particularly personal wikis) there is little to no use of Access Control Lists (ACLs) and/or no need to restrict access between pages.
As the default is undefined (false) this means that unless specifically granted access these plugins will not introduce a new inter-page security issue.
If you or your users wish to use ACLS and wish to respect the privacy they create, don't set the 'open wiki' flag to true (his is the default setting). Likewise, plugins that use this feature should provide notification in their user documentation, to indicate they pay attention to this flag.
These are the displays produced by the plugin (i.e., static content, not the plugin itself):