Symptoms
Event Viewer contains 'URL authorization failed for the request' errors.
Cause
This can happen when someone logged in with a valid customer account attempts to access the admin portion of the site. While they have an account, they are not authorized to access that portion of the site, so the error is logged.
Solution
This will generally only happen during testing as site visitors should not be able to guess the admin URL if our security best practices have been followed. As long as those practices are followed, there is no security risk.