Protecting Against Malicious OAuth 2.0 Applications: Best Practices

Read full article here:  https://www.slashid.com/blog/oauth-chrome-extension-breach/?source=nhimg

A recent wave of compromises targeting Chrome extension developers has once again highlighted the risks of malicious OAuth 2.0 applications. The attackers, believed to be state-sponsored groups such as APT29, weaponized rogue OAuth apps to phish developers and gain access to Google accounts, enabling them to publish backdoored extensions.

At the core of the problem is trust. OAuth 2.0 allows third-party applications to request access tokens and act on a user’s behalf. While this design powers modern integrations, it also opens the door for abuse if users grant access to a malicious app. Once authorized, attackers can exfiltrate data, impersonate accounts, or, in this case, inject malicious code into the Chrome Web Store.

Key Risks

• OAuth 2.0 apps can impersonate users once tokens are granted.
• Attackers can bypass provider verification checks.
• Risky scopes (such as publishing rights) are often overlooked in admin reviews.

How organizations can defend

1. Regularly review authorized apps across identity providers (Google, Microsoft, Okta, etc.).
2. Scrutinize requested scopes — broad or unusual permissions should raise red flags.
3. Automate detections for anomalous OAuth usage and risky scopes.
4. Revoke suspicious grants quickly through identity provider APIs or remediation playbooks.

How SlashID helps

• Maps which users are tied to which OAuth apps via its Identity Graph.
• Provides built-in detections for risky scopes and suspicious apps.
• Enables fast remediation by revoking malicious access in real time.

As MFA and traditional phishing defenses improve, attackers are pivoting to OAuth-based phishing, exploiting the very frameworks meant to simplify secure access. Security teams must adapt quickly by monitoring, detecting, and containing these new attack vectors.