According to various embodiments, the Message Authentication Engine is given permission to access dynamically changing content provided by a buyer system. The Message Authentication Engine receives a purchase request from the buyer system for an item from a vendor system. Based on the purchase request, the Message Authentication Engine retrieves a portion of the dynamically changing content from a client device of the buyer system. The Message Authentication Engine provides to the vendor system the portion of the dynamically changing content provided by the buyer system. The vendor system sends a message to the buyer system with a copy of the portion of the dynamically changing content as a visual verification that the vendor system can be trusted.