2022 Annual Penetration Testing Intelligence Report. Read Now

28 November, 2022

What is API Penetration Testing?

What Is API Penetration Testing?

Application Programming Interfaces (APIs) play a critical role in the age of digital transformation, catalyzing software and app development for DevOps teams at an unparalleled level of acceleration. APIs save developers time, improve system scalability and flexibility, lower development costs, and increase go-to-market speed. Although APIs can be the greatest thing since sliced bread when leveraged correctly, they can add another layer of security risk into the mix – which is why API penetration testing is important.

In this article, we’ll cover the essentials of what an API is, what an API pen test is, and how it strengthens API security and compliance.

What is an API?

An Application Programming Interface (API) offers the ability for an organization to extend their hosted web services and provide interfaces for automated services, like Single Sign-On (SSO), to their customers, partners, and third-party suppliers. An API usually provides everything that an organization’s web application would provide – except without the graphical interface. The function of an API is to answer automated requests typically handled by processes versus human beings. These processes may be vulnerable and could introduce a security threat to the API’s hosted cloud environment, or the API itself may be vulnerable. Therefore, it’s imperative, and in many cases, a regulatory requirement, to conduct an API penetration test to ensure the API security standards are met.

What is an API Penetration Test?

An API penetration test is an application penetration testing exercise performed by certified human hackers in a controlled environment simulating a cybersecurity attack on an API endpoint. API penetration testing is considered an industry-standard offensive security practice that enables organizations to meet security compliance requirements (i.e., PCI DSS, SOC 2, ISO 27001, GDPR, and HIPAA) and improve their security posture to protect their sensitive and regulated data, systems, and processes.

With a trusted API penetration testing service provider, an organization can securely and safely scan for vulnerabilities on its API endpoints. A trusted API pentesting vendor will have ethical hackers with relevant certifications, like the OSCP, CEH, OSCE, CREST, CISSP, or GSNA. Benefits will include expert remediation guidance and customer support to formulate a risk remediation plan that helps meet compliance, builds cyber resiliency, and improves overall security posture. Qualified, experienced pen testers will know how to test for API vulnerabilities without introducing additional risks, and they will confirm with the organization the users, roles, resources, and responses of the APIs before testing them.

What Vulnerabilities Does API Penetration Testing Uncover?

In the scoping part of the pentest engagement, a pentester will outline their hypothesis and details of what they think the hacker would want to target through the organization’s API. This determines how the pentester will conduct vulnerability scanning for the API test environment. The scope confirms the process and methods the pentester will use to discover potential security risks that could be exploited by a hacker.

When API penetration testing is conducted, pen testers generally leverage the OWASP API Top 10 first for discovery guidance:


  • M1: Improper Platform Usage
  • M2: Insecure Data Storage
  • M3: Insecure Communication
  • M4: Insecure Authentication
  • M5: Insufficient Cryptography
  • M6: Insecure Authorization
  • M7: Client Code Quality
  • M8: Code Tampering
  • M9: Reverse Engineering
  • M10: Extraneous Functionality

The most common vulnerabilities listed in the OWASP API Top 10 offer a great start for an API pentest, but that is just the beginning. Penetration testers should test for more than those ten vulnerabilities. Experienced penetration testers will apply business logic and a hacker’s perspective to any API penetration testing exercise that they conduct to ensure they are testing the API endpoint for all potential critical risks in the API’s ecosystem.

In the Annual Penetration Testing Intelligence Report, BreachLock analyzed the results from over 8,000 penetration tests conducted in 2021. Out of the APIs that were tested, the most common critical and high-risk vulnerabilities discovered in APIs were:

  • OAuth Token Misconfigured to Account Takeover
  • Remote File Inclusions (RFI)
  • Log4Shell Vulnerable
  • Function-Level Access Control Missing (which accounted for 47.55% of the findings in this list)
  • SQL Injection
  • Apache Path Traversal (CVE-2021-41773)
  • Account Lockout Policy Issue
  • Account Takeover

Not all API environments will have the same vulnerabilities to remediate. Having an experienced pen test provider with experienced hackers that can conduct in-depth testing and analysis comes into play here. Not all vulnerabilities are ‘known’ or published CVEs. With a trusted penetration testing service, the penetration testers gather more context on the customer’s environment with every engagement. Delivering more than one pentest report, these reputable providers will have a vested interest in the overall security of their customers over time. API pentest engagements will go beyond the typical use case scenarios to ensure all potential exposures are tested, and remediation guidance will be integrated with more context of the organization’s digital ecosystems. Once the critical findings are delivered, DevOps remediation can be prioritized to improve any discovered API compliance vulnerabilities and security gaps.

When is it Time for an API Penetration Test?

APIs are a great tool for developers to accelerate their development process. However, they introduce a whole new layer of security risk, which is why routine API penetration testing is so important.

API pentesting is always initiated with a clear objective in place, which could be several things. The most common reasons why organizations initiate API penetration testing are compliance requirements (SOC 2, HIPAA, GDPR, ISO 27001, PCI DSS, etc.), third-party security requirements, and vendor assessments, which are often needed to earn or retain high-value clients. Although those are all use cases that require organizations to schedule an API penetration testing engagement. Meanwhile, many businesses prioritize routine penetration testing as a major part of their overall offensive security strategy and GRC (governance, risk, and compliance) program. Routine penetration testing gives organizations leverage over outside threat actors by allowing them to find and fix vulnerabilities before threat actors even get the chance to try exploiting them.

Routine penetration testing in the SDLC is not only a good idea, but also prevents the likelihood of a costly, business-crushing breach later in production. Prior to launching an initial application release or a major update, product managers and engineering teams work together with security leaders to conduct an API penetration test. Then, teams work together on remediation guidance as part of their DevOps / DevSecOps workflows. A few benefits here are achieved: DevOps teams that can remediate risk quickly and early on are less likely to be pulled away from important projects later to patch vulnerabilities. Furthermore, testing earlier and often in the CI/CD pipeline not only shifts security left, but it also reduces the likelihood of a breach occurring later in production environments, when breach costs are much greater – including lost customers and costly regulatory fines. Finally, pentesting API security within the SDLC strengthens cyber resilience and sets the stage for compliance readiness for security audits.

API penetration testing doesn’t necessarily have to be “triggered” by a major milestone either – enterprise-level companies are known to be consistently vigilant in monitoring their attack surface closely to manage risk. These larger organizations are notoriously targeted by threat actors, which requires them to always stay one step ahead of them. Organizations that take their security posture seriously value attack surface visibility as a major component of their offensive security practices. API pentesting can offer continuous visibility to emerging threats and zero-day vulnerabilities.

How Long Does API Pentesting Take?

Part of the answer to this question is that the lead time for API penetration testing depends almost entirely on the scope of the project. For API penetration testing specifically, the scope is determined by the number of API endpoints connected to the organization’s mobile or web application. As you’d assume, the more API endpoints that need to be examined, the longer the API penetration testing engagement will take. However, there are some generalizations that can be made about the lead time you can expect for your API penetration test when choosing your penetration testing provider.

Traditionally, API penetration testing was done with a 100% manual, consultancy-based model that took traditional testing providers months to deliver reports to eager-to-learn security leaders. Luckily, there are better options available today that can deliver results within a week or less, thanks to Open-Source Intelligence (OSINT) and innovators in the pentesting space. The pitfalls of the traditional approach are easy to bypass when compared to the power of AI-driven automation, human expert analysis, and built-in remediation guidance.

So, how is an API Penetration Test conducted?

It depends on the penetration testing provider.

For years, security leaders have grappled with the traditional model of penetration testing, which grants access to third-party vendors (and third-party security risks) – from freelance hackers to large consultancy firms. High costs, long lead times, and inability to scale for bulk pentesting are issues that historically stalled product launches and DevOps remediation. Furthermore, leaders have struggled to source pentesting providers that integrate DevOps remediation into the pentesting lifecycle

Old school pentesters must search for each vulnerability one by one and report on findings using manual techniques. These outdated methods cause delays, which stall critical vulnerabilities from being remediated – increasing key MTTx metrics for security, such as “Mean Time to Remediate.” Slow report turnaround time with minimal remediation guidance adds workflow friction and contributes to DevOps remediation delays. All of these issues increase the overall exposure windows for API vulnerabilities discovered by traditional pentesting providers, which increases their likelihood of exploitation.

A better way to conduct API pentesting exists today. Coined as Penetration Testing as-a-Service (PTaaS) by market leaders, the PTaaS approach cuts traditional API pentest turnaround time and costs in half by combining manual techniques with AI and automation. API pentesting that incorporates AI and automation is a smart way to leverage skilled, hard-to-hire penetration testers. These automations relieve pentesters by offloading simple tasks and easy-to-find vulnerability discoveries in APIs so that they can instead focus on eliminating false positives with manual validation and uncover more difficult, contextual vulnerabilities with their skills, experience, and creativity.

What Tools do Pentesters Use for API Penetration Testing?

When conducting API penetration testing with the modern PTaaS approach, artificial intelligence (AI) and automation tools are combined with manual testing techniques to increase penetration testing velocity. Since Open-Source tools are plentiful in the modern world, and AI has become increasingly prominent, especially over the past decade, advanced penetration testing providers leverage these tools as much as possible in order to scale their most scarce resource – technical talent.

The cybersecurity talent gap continues to widen year-over-year, with recent research revealing that 3.4M cybersecurity roles are unfilled around the world in 2022. Time is of the essence when it comes to the skilled talent that companies have for 24/7 network monitoring in security operations. Penetration testing providers have to pull out all the stops to make sure that their customers are getting the most value possible from their security team’s time during API penetration testing engagements.

During API penetration testing exercises, penetration testers utilize tools like Burp-Suite Professional, Swagger UI, Curl, Nmap, and Custom Scripts – and sometimes proprietary technology, depending on the provider. In BreachLock’s case, a cloud platform with a SaaS client portal offers customers a single pane of glass to see their pentesting reports and action on remediation guidance for actionable results and customer support through the portal. Using these tools frees up a penetration tester’s time so they can dig deeper when searching for vulnerabilities.

BreachLock’s Take on API Penetration Testing

Today’s growing threat landscape demands rigorous testing of API endpoints for security risks that could impact its digitally connected ecosystem, users, and data. BreachLock offers an alternative to traditional penetration testing with advanced API pentesting with PTaaS. With PTaaS, organizations can start routine API pentesting in one day, get findings in 7-10 days, and begin remediating critical risks right away, with expert guidance from BreachLock-certified customer support.

Ready to see how you can easily and quickly remediate security risks in your API? Schedule a discovery call today and learn how BreachLock’s API pentesting service and PTaaS can support your security and compliance outcomes today.

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