Since I upgraded from 5.24.4 to CiviCRM 5.28.2, roughly since end of August 2020, I have been finding a lot of errors in the log when Anonymous users attempt to access mysite.com/civicrm/mailing/url.
- If I go to this URL myself (as an admin) I get the CiviCRM error box with the message
"Error: Could not find valid value for u".
- If I go there as Anonymous I get the same error message on a blank white screen.
- On 5.24.4 Anonymous gets 'Access Denied' which is sensible, and Admin gets a list of current mailings.
What should this URL do?
Presumably 5.28.2 has introduced a bug?