OAuth2 Provider service's "Token Signing HMAC Shared Secret" is lost during the upgrade from OpenAM 13.5.0 to AM 6.0.0. I would assume that this affects others upgrade paths between.
- Install OpenAM 13.5.0
- Configure OAuth2 Provider Service and enable stateless OAuth2 tokens
- Configure OAuth2 client
- Obtain an access token and keep a reference to the returned JWT
- Upgrade to AM 6.0.0
- Call the /tokeninfo endpoint for the access token created prior to the upgrade
Manually re-entering the value for OAuth2 Provider service's "Token Signing HMAC Shared Secret" fixes the configuration.