SagePay Suite Admin/Backend (MOTO) payments don't work after SUPEE-11314

SagePay Suite Admin/Backend (MOTO) payments don’t work after SUPEE-11314 or upgrade to Magento 1.9.4.5. The following error is logged:

Server error 5006: Unable to redirect to Vendor's web site. The Vendor failed to provide a RedirectionURL.

Cause

Admin SID (Session Identifiers) were disabled in SUPEE-11314 and 1.9.4.5 version and Sage Pay Suite MOTO payments makes use of Admin SIDs to process payments.

Solution

Re-enable Admin SIDs, to do this properly you can insert the following record in `core_config_data`:

mysql> insert into `core_config_data` (scope,scope_id,path,value) VALUES ('default',0,'web/session/use_admin_sid',1);
mysql> select * from `core_config_data` where path like 'web/session/use_admin_sid';
+-----------+---------+----------+---------------------------+-------+
| config_id | scope   | scope_id | path                      | value |
+-----------+---------+----------+---------------------------+-------+
|      1509 | default |        0 | web/session/use_admin_sid | 1     |
+-----------+---------+----------+---------------------------+-------+

Alternatively, use instructions from this article on how to re-enable use of Admin SID in Magento.