You will need to use the Bugzilla "bug" reporting system.
Get started by searching to see if your issue has already been reported by using the issue submission gateway, using the search box at the top left of the page. Searching issues with Bugzilla does not require an account.
To update existing issues (for example, add your findings to an existing issue), or file a new issue, you will need a Bugzilla account. Register with Bugzilla using the New Account link. Once you obtain your Bugzilla login, you can return to the issue submission gateway to update issues or enter new ones. Or, use the default Bugzilla interface.