Looks like the redirect_url passed to authentication loses the state parameter if the user has to log in during the process. If the user is already logged in the state parameter remains as expected.
https://app.hubspot.com/auth/authenticate?client_id=<client_id>&redirect_uri=https%3A%2F%2Fapp.influitive.com%2Fintegration%2Foauth%2Fcallback%3Fapikey%<api_key>%26state%3Dhubspot%253A%253Aapp
For example, this oauth request would redirect to the following if they were not already logged in: https://app.influitive.com/integration/oauth/callback?apikey=<api_key>
