Radius module pad extra backslash to user password

I got a strange problem when user can login via webUI but not via radius plugin. Both method authenticate against an AD backend. Find out that if the user’s password have a backslash \ the privacyidea will add an extra one to the password before send it to AD.
My PI version is 2.20.1.
Is it bug or I’ve messed somewhere else?

Thank you,

This sounds like RADIUS!

Stop freeradius and then run freeradius in Debug mode via:

freeradius -X

You should see, how the password looks like.

Thank Cornel,
You’re right. It’s freeradius problem. I’m using freeradius 2.2.8+dfsg-0.1ubuntu0.1 shipped with Ubuntu 16.04.3.