Check referer issue in multiple versions 0.8.4, 0.9.0, and 0.9.1

[jamil_isayyed]

Hello folks,
i am facing a problem with the config check_referer , when this option is enabled i am getting an error.
when the user opens a pdf attachment i get this error:

"
REQUEST CHECK FAILED

Access to this service was denied due to failing security checks!
Please contact your server-administrator.
"

so please any advise how i can fix this issue.

Thanks in advance.
BR,
Jamil Isayyed