This papers discusses security and the REST API. Specifically discussed is a security implementation using OAUTH as part of the security framework to protect access to resources (data and services).
You can download it from the following link: https://packetstormsecurity.com/files/download/135132/Oauth_Security_Issues_Rest_API_authentic.pdf
Source: https://packetstormsecurity.com/files/135132/OAUTH2-Security-In-The-Representational-State-Transfer-API.html