When running a Web Agent protecting one application, and redirecting requests to another Web Agent, then the request fails to say that the URL is too long. Has there been security concerns to raising the IIS MaxURL to 8k?
There are any known security concerns from SiteMinder documentation, and Microsoft documentation either. It seems there's no limit to the value according to Microsoft (1).
More, some experiences have been reported where IIS maxQueryString configuration might help to handle long URLs (2)(3).
The feature maxURL is something from IIS functionality (1).
There's no known limit on the Web Agent level.
There's no feature known as MaxURL for Apache.
Be aware that there are some limitations on Apache and also in the browsers too (4)(5).