On July 22 everything was running smooth and fine. Starting on July 23rd all I’m receiving is an error of 403 (forbidden). I can use my client and secret from here without any issues. I’m using the latest secret. I’m only experiencing this issue while running them through my app.
Example call: /data/wow/connected-realm/117
Anyone else experiencing this issue?
Unless you re-generated the secret there is no “latest” secret. Did you mean access_token ?
Each token lasts for 24h only, your app must properly implement the OAuth2 client_credentials flow to keep your token updated.
Hi, got the same error starting July 23rd. Did you find any solution @Nimue ? 
Of course i generate a new access token each time 
I found a solution to my problem: they changed the URL from https://eu.battle.net/oauth/token to https://oauth.battle.net/token. Maybe this will help you as well — or maybe I was just using the wrong URL from the beginning.
I only started getting this error when my redirect URI is localhost, but still works when using a public URI and its associated client ID.
I’m using this as redirect URL https://eu.battle.net/login/en/?ref=https://oauth.battle.net/oauth/authorize
and then add all the required parameters as specified in their API docs.
EDIT: The ‘Example flow’ section in their API docs worked for me:
https://develop.battle.net/documentation/guides/using-oauth/authorization-code-flow