Systems and methods of the present invention provide for one or more server computers communicatively coupled to a network and configured to: identify, within a data store: a web page including a script tag; and a URL in the script tag referencing a location for a second server hosting a script file. The server computer(s) execute a request that accesses the script file and a signature file generated by a private key, associated with the script file, and stored on the second server computer. If the signature file contains a signature that cannot be authenticated using the public key associated with the private key, execution of the script tag is disabled, and a notification is generated.