Systems and methods for injecting sensitive data into outgoing traffic on behalf of a user of a private network are provided. According to one embodiment, a network security appliance maintains a database of sensitive data. Secure submission of sensitive data of a user is facilitated by the security appliance in connection with interactions between a client and a server by: (i) intercepting outgoing traffic from the client to the server; (ii) determining whether the outgoing traffic matches a policy configured by an administrator of the private network that causes the sensitive data to be injected into the outgoing traffic by the network security device on behalf of the user; and (iii) when the determining is affirmative: (a) retrieving the sensitive data from the database; (b) modifying the outgoing traffic by injecting the sensitive data into the outgoing traffic; and (c) sending the modified outgoing traffic to the server.