System and methods for injecting content into a response for improving client-side security. The system includes a content injection service external to network edges of at least one system. The content injection service receives a request from a client within the at least one system and identifies or anticipates a potential threat associated with the response. The content injection service is configured to determine an appropriate counter for the identified or anticipated potential threat and in response injects content into the response according to the potential or anticipated threat identified.