Configurations for sharing an instance of an executing process for a plug-in based on a session and a cookie data store associated with the session are disclosed. A cookie data store can be associated with a tab running in a corresponding security mode. By way of example, instead of initiating a new process for the plug-in in a new tab, the subject technology can first determine whether a previous tab is running an instance of a plug-in process. If this is the case, the subject technology can then determine whether the previous tab is running in the same security mode (e.g., protected or unprotected) as the new tab. The subject technology then shares the existing plug-in process in the previous tab without instantiating a new plug-in process in the new tab.