How can we restrict access to CLM/RQM to validated browsers?

I'm not aware of any 'built it' way to accomplish (others my chime in); in theory , you could set up a filter based on the User-Agent string

User-Agent

This may be a helpful link

http://www.tomcatexpert.com/ask-the-experts/useragentvalve

"By examining the user agent string, it's possible to filter out specific browsers and versions. IE strings are found here. The user agent string is sent from browsers as a HTTP request header with every HTTP request. It's also available via javascript for client side code.

On the server side, one way to filter is by writing a custom Valve which examines the user agent string. However, Valves are Tomcat specific, and are relatively rare in the field. So writing a valve may lead to code maintenance issues in future."