RSS Security key page is visible for each user. Normal user and most admins won't understand the page without additional information.
Security aspects that user don't understand may become a security aspect. Its not a classical security problem
Todo: add a text string below headline RSS
Information text draft:
RSS Feeds can be used to read content from your course in external RSS Feed Readers if these feature is enabled in your Moodle system. Moodle supports individual security keys for these links to protect access for the content.
You can reset your personal "Security key" if you think it is abused or available for other users.