1. A method of facilitating secure commenting on content items among collaborators via external messaging applications in a collaborative cloud-based environment, the method comprising: receiving a response to a notification associated with a content item from a collaborator via an external messaging application, wherein the response includes a text-based comment associated with the content item and secure message information provided by the notification including a message and a message authentication code; and determining a validity of the response, wherein determining the validity of the response includes verifying the integrity of the message using the message authentication code.