You are processing with Authorize.net, and have enabled the Fraud Detection Suite. You have found certain credit card transactions marked Incomplete in the Orders Report and want to complete the review.
These Incomplete transactions show a Payment Reference like: For security reasons your order is currently being reviewed.
Under Reports -> Orders -> Payment History for the order in question, you can see the transaction details, in particular the transaction ID. Search for this transaction ID in Authorize.net and/or refer to this number if you contact them by phone.
After reviewing with Authorize.net, you can mark the order(s) in question as Complete by following the directions at How do I charge an Incomplete Credit Card Order?