Broken Authentication and IDOR – A Big but Solvable Problem

Broken authentication and IDOR (Insecure Direct Object Reference) attacks remain two of the most reliable paths for attackers to move laterally, steal data, or take over accounts. Despite topping the OWASP Top 10 (as broken access control) they continue to show up in breach reports because engineering teams often underestimate how easy they are to exploit. Beyond reputational harm, a single weak login flow or exposed identifier can also put compliance efforts at risk with frameworks like SOC 2, HIPAA, or ISO/IEC 27001. To strengthen both security and audit readiness, it’s critical to understand how these vulnerabilities work, where they hide in modern applications, and how to systematically prevent them.

What Is Broken Authentication?

Broken authentication vulnerabilities occur when attackers can bypass or abuse authentication mechanisms. According to the OWASP Top 10 (which is being updated in late 2025 - exciting!), these weaknesses are among the most common causes of breaches. Attackers often rely on weak passwords, failed login attempts, brute force attacks, or stolen credentials to compromise user accounts and gain access to sensitive data.

Broken Authentication through Credential Stuffing

Credential stuffing uses stolen username and password pairs from previous breaches to gain access to new accounts. If a user reuses credentials across platforms, attackers can often succeed. This technique is one of the most common broken authentication attacks.

A Solution – MFA

MFA makes credential stuffing far less effective by requiring an additional proof of identity beyond a username and password. Even if stolen credentials are correct, access is blocked without the secondary factor.

Preventing credential stuffing attacks is entirely possible. The recommended defense to this attack and several others by NIST SP 800-63 is Multi-Factor Authentication (MFA). If an identity/password combination could work, but there is also a need to have the phone or device that will generate a one-time password, then the bad actor’s access is made considerably harder.

An Alternative Solution – Secondary passwords

Secondary credentials (like a PIN or security question) and CAPTCHAs add friction for attackers, though they are not as strong as MFA. CAPTCHA helps block automated brute force attempts, while secondary passwords can reduce—but not eliminate—risk.

Alternative Solutions: Secondary passwords and CAPTCHAs

Secondary credentials (like a PIN or security question) and CAPTCHAs add friction for attackers, though they are not as strong as MFA. CAPTCHA helps block automated brute force attempts, while secondary passwords can reduce—but not eliminate—risk.

Session Hijacking and Brute Force Attacks

Beyond credential stuffing, attackers may exploit broken authentication through brute force attacks or session hijacking.

• Brute force: Attackers repeatedly attempt login combinations until they succeed.
• Session hijacking: Attackers steal active session tokens to impersonate a user. Strong access control checks, failed login monitoring, and secure session handling are critical defenses against both methods.

What is an IDOR Attack?

An Insecure Direct Object Reference (IDOR) occurs when an application exposes identifiers such as userID, recordID, or file paths without proper access control checks. Attackers can manipulate these references to gain access to data or functionality they should not see.

For example, if a web application allows users to retrieve invoices by changing a query string like:

/invoice?userID=123

an attacker could increment the ID to 124 and access another customer’s invoice if the server doesn’t validate ownership. This is a prime example of an attack scenario that may expose personally identifiable information (PII) listed on the invoice document for all users in the database. Although these techniques are trivial, they can result in disastrous and rapid data breaches.

These broken authentication vulnerabilities often arise from developers assuming identifiers are obscure enough to provide security, when in reality they’re easily guessable. Thankfully, these are becoming rarer.

How to Mitigate IDOR Vulnerabilities

• Server-Side Validation: Never rely on client-side checks. Always confirm on the server that the user is authorized to access the requested resource.
  
  
• Least Privilege Access Controls: Ensure every request enforces strict authorization rules tied to roles, not just user IDs. Zero trust approaches to identity can take this good idea and take it even further.
  
  
• Use Non-Sequential Identifiers: Replace predictable values with salted hashes, UUIDs, or opaque tokens that are difficult to guess. Although obfuscation can help reduce risk, attackers may still be able to access restricted resources by learning these values via other methods.
  
  
• Centralize Access Control Logic: Inconsistent or scattered authorization checks often lead to oversights. Consolidating them reduces risk.
  
  
• Testing and Continuous Validation: IDORs are notoriously missed in static testing. Incorporating bug bounty programs or vulnerability disclosure programs helps catch real-world attack patterns.

By combining secure coding practices with continuous external validation, organizations can detect object reference flaws before attackers do.

Learn more about how a Vulnerability Disclosure Program supports this process by allowing good internet citizens to see something and say something to software developers.

Continuous Testing and Bug Bounty Programs

Inspectiv works with thousands of vetted security researchers to uncover broken authentication vulnerabilities and IDOR attacks in real-world conditions. Through bug bounty programs and dynamic application security testing, security teams gain continuous visibility into risks across web applications.

Learn more about how Inspectiv’s Bug Bounty program provides validated findings that reduce noise and help teams focus on remediation that matters.

FAQs on Broken Authentication and IDOR

What does "broken authentication" mean?It refers to flaws in login or session management that allow attackers to bypass identity checks.
What is an IDOR attack?

An IDOR attack exploits exposed object references, allowing attackers to access unauthorized resources.


How can I mitigate IDOR vulnerability?

Enforce strict access control checks, validate every request server side, and avoid exposing raw identifiers like user IDs.


What are the 5 common authentication problems?

Weak passwords, credential reuse, session hijacking, brute force attacks, and improper access controls.Moving Toward Stronger RemediationBroken authentication and IDOR are not abstract risks, they are attack vectors actively exploited in the wild. The good news is that with the right mix of engineering discipline, access control enforcement, and continuous external validation, these vulnerabilities are highly preventable. Inspectiv gives security teams a clear advantage by pairing dynamic application security testing with bug bounty programs to surface validated, high-impact issues that engineering can act on quickly.Ready to see how Inspectiv can help? Schedule a demo today and see how our platform uncovers and prioritizes vulnerabilities before attackers do.