Open Authorization (OAuth), is a widely used protocol for allowing third-party SaaS to access resources from a user's accounts, devices, and identities on a web service, without the need for the user to share their login credentials. It works by enabling the user to grant permission to the third-party application to access the web service on their behalf (e.g., SaaS services), using an access token. Rather than giving an application full login credentials, OAuth allows it to act on the user's behalf with a temporary access token, minimizing the risk of password exposure and misuse.
OAuth separates the roles of resource owner (the user), client (the app requesting access), authorization server, and resource server. Here’s a simplified flow:
1. User Requests Access
A user initiates a request to access a third-party app or service using an existing account (e.g., “Log in with Google”).
2. Authorization Prompt
The user is redirected to the identity provider (e.g., Google, Microsoft) and asked to approve the permissions the third-party app is requesting.
3. Access Token Issued
Upon user consent, the authorization server issues a short-lived access token to the third-party application.
4. Token-Based Access Granted
The third-party app uses the access token to interact with the user’s data without ever seeing their password.
OAuth tokens are scoped, meaning they provide only the specific permissions the user approved, and they can be revoked or expire, adding an extra layer of control and security.
OAuth is a cornerstone of modern identity and access management, particularly in SaaS ecosystems, where users often connect multiple services and applications. It enables secure interoperability between apps while maintaining user control over data sharing.
However, OAuth also introduces new risks if not implemented carefully:
Security teams must monitor and audit OAuth usage to ensure only trusted apps are granted access and that scopes are appropriately limited.
It’s a common misconception that OAuth is an authentication protocol. OAuth is primarily a delegated authorization framework—it doesn’t authenticate users directly but is often used in combination with protocols like OpenID Connect (OIDC), which sits on top of OAuth to provide secure user authentication.
While OAuth is designed to give users fine-grained control over what third-party applications can access, in practice, OAuth scopes can often become overpermissioned, granting more access than necessary. Scopes define what level of access an app is requesting, such as reading emails, accessing files, or managing calendar events. However, users frequently accept these permission requests without understanding their implications.
When applications are granted broad or excessive scopes, it significantly increases the potential blast radius of a breach. If a malicious or compromised app has access to sensitive data across multiple SaaS platforms, attackers can exfiltrate large amounts of information using valid tokens without ever needing to compromise a password. See how OAuth attacks are used to access sensitive systems.
In many environments:
This creates a hidden layer of SaaS identity risk that most security teams don’t monitor closely. In the event of a compromise, OAuth-based access can be exploited to move laterally across applications, access confidential data, and bypass standard IAM controls, all under the guise of a “trusted” integration.
To reduce this risk, organizations should:
By managing OAuth scopes with the same rigor as traditional access permissions, security teams can limit potential exposure and maintain tighter control over data access across SaaS environments. See how Grip identifies and manages OAuth permissions.
OAuth is a powerful and widely adopted standard for secure, delegated access in web, mobile, and SaaS applications. By enabling token-based authorization without exposing user credentials, OAuth enhances both usability and security. Organizations should treat OAuth scopes, tokens, and integrations as critical parts of SaaS security posture management, auditing regularly to prevent misuse and reduce identity-related risks.
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The Rise of OAuth Attacks to Access Sensitive Systems
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