A canary value is used to validate a message from a non-web browser client application to a web server providing web services to mitigate cross-site forgery attacks. The canary value is generated by the server in party by applying a hash function to a user identifier and a time stamp. The server provides the canary value to the client application in response to receiving a message that does not have a canary or has an expired canary. The client application upon receiving an error message with a canary message will resend the prior message with the canary value present. The client application caches the canary value for subsequent messages until a new canary value is received. The canary value allows the server to ignore messages generated by the client application under control of an attacker.