Login redirection doesn’t work correctly

To reproduce:
* Enable the Custom Redirection module
* Configure the following custom login redirect via the Theme My Login Custom Redirection Settings page: https://www.example.com/?a=1&b=2&c=3
* Login

Expected: Should get redirected to https://www.example.com/?a=1&b=2&c=3
Actual: Get redirected to https://www.example.com/?a=1

We’re on version 6.4.17.

I think the issue is that the redirect_to query parameter value is not being urlencode()’d when add_query_arg() is called in class-theme-my-login.php, line 525.

If this is a bug, is it possible to make a 6.4.x release? We’re not able to upgrade to 7.x.

Thanks for your help, much appreciated.