[imp] Error: "Required secret is invalid - potentially malicious request"

[Babita]

Hi, our users are seeing the following error message on a blank screen 
when they hit the logout button:

"Required secret is invalid - potentially malicious request."

Any idea as to why this is error pops up and what can be done to prevent 
it?

We're using Horde 3.2.1 & IMP H3 4.2.

And kudos to the development team for your open source software and your 
time answering our questions ;)

--
Babita Rana
AICT
University of Alberta