Implementations of the present disclosure include methods, systems, and computer-readable storage mediums for user confirmation of actions to be performed by a web application hosted on one or more servers. Actions can include receiving user input indicating a request directed to the web application, the user input being received through a mobile web browser, determining that the user input is requesting execution of an authorized action, and in response, providing data associated with the request for processing by a mobile authenticator application, providing a user interface generated by the mobile authenticator application based on the data, and receiving user confirmation of the authorized action through the user interface, and in response: providing a signed response by the mobile authenticator application, and transmitting the signed response to the one or more servers to initiate execution of the authorized action.