The source editor transcludes [[MediaWiki:Editpage-head-copy-warn]] above the edit window. But this does not appear anywhere when using the visual editor.
Note this is distinct from [[Mediawiki:Copyrightwarning]] which appears (in a tiny font) in the edit summary tool. The two messages are not the same and do different jobs - the first is a warning that copyrighted content is not acceptable and content must be verifiable, the second is a statement that by saving you release your contributions under cc-by-sa.
Version: unspecified
Severity: minor