May 11, 2015 · OAuth works over HTTP and authorizes Devices, APIs, Servers and Applications with access tokens rather than credentials, which we will go over in depth below. There are two versions of OAuth: OAuth 1.0a and OAuth2. 2017-12-01 13:53:52,714 ERROR ru.atc.esia.oauth2 [ru.atc.esia.aas.oauth2.server.filter.AuthzCodeEndpointFilter:126] Requested scopes not permitted...Working with OAuth. OAuth is a secure means of authentication that uses authorization tokens rather than a password to connect your app to a user account. Initiating OAuth access is the first step towards allowing users to install your app in their HubSpot account(s). OAuth 2.0 Errors. Authorization Response Error Codes. Token Response Error Codes. Definition of errors of issuing Access Token in the RFC6749 standard.