Article: Identifying valid API keys

The following repository shows some ways of how particular API keys (found by e.g. searching on Github) can be validated.
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Service Request
Slack curl -sX POST ""
Slack Webhook curl -s -X POST -H "Content-type: application/json" -d '{"text":""}' ""
Facebook AppSecret
Facebook Access Token
Firebase curl -s -XPOST -H 'content-type: application/json' -d '{"token":":custom_token","returnSecureToken":True}' ''
Github curl -s -H "Authorization: token TOKEN_HERE" ""