Systems and methods, including computer software adapted to perform certain operations, can be implemented for providing remotely defined security data to an application extension on a client device. A sequence of instructions and at least one permission indicator associated with the sequence of instructions are received. A first permission indicator is associated with a code extension to a software application adapted to execute at least a portion of the sequence of instructions. The code extension is adapted to perform one or more operations that supplement the operations supported by the software application. An instruction within the sequence of instructions associated with adapted for execution by the code extension and with an activity is identified. The first permission indicator is provided to the code extension. The code extension determines whether performance of the activity is permitted based, at least in part, on the first permission indicator.