Your business most likely thrives on application programming interfaces (APIs). They power your innovations, connect your services and enable you to deliver unique value to your customers. But this explosion of APIs, while fantastic for growth, often comes with a hidden and tangled shadow side. 

And this is where the challenge of API sprawl begins to surface. It manifests as a growing, often unacknowledged, collection of APIs that outpaces an organization’s ability to effectively track, manage and secure them, leading to a digital infrastructure where visibility is lost and control feels increasingly elusive. 

Basically, any API that is either undiscovered or still running but unaccounted for falls into the category of a shadow API or a zombie API. These aren’t just abstract terms; they represent real and distinct security vulnerabilities. 

Shadow APIs are those operating completely off the radar. They are undocumented — no one knows they exist. If someone created the API, there is no record of it, no documentation and no one ever came across it again. As a result, the security team never gets this information. No security review or vetting ever takes place. 

Zombie APIs, on the other hand, are those that should be gone but aren’t. Say you might have an API that gets replaced or moved to a new subdomain, but the old one is never decommissioned. The danger lies in the fact that both versions are still alive. And even if they are considered deprecated or ‘not in use’, the reality is that they still work. 

In both cases, the core issue is that security teams don’t know these endpoints exist. So, they are never tested, monitored or patched, leaving them wide open to exploitation. 

Akash Agrawal, VP of DevOps & DevSecOps at LambdaTest, an AI-Native software testing platform, highlights the neglect these often face. “Zombie APIs typically lose engineering support during the deprecation period, meaning no engineers are patching the APIs or doing any security improvements to them. Shadow APIs might have been spun up for an internal team, and they forgot about it completely — it is just lying around.” 

This, Agrawal says, creates a fertile ground for security vulnerabilities that often go unnoticed until it is too late — because the implications of API sprawl extend far beyond mere operational untidiness. They pose significant, and often underestimated, security risks. 

Where Security Starts Going Wrong 

When shadow and zombie APIs operate outside normal oversight, they don’t just represent a messy inventory — they expand the attack surface with new vectors and vulnerabilities. Without visibility or clear ownership, the consistent application of security basics often falls by the wayside, leaving organizations dangerously exposed. 

The most immediate danger is how this sprawl spurs wildly inconsistent security postures across the API landscape. Siri Varma Vegiraju, security tech lead at Microsoft Azure Security, points out that when APIs proliferate unchecked, critical controls are easily missed. “When you have a bunch of APIs, and if it is done quickly, what people don’t add to those APIs is proper authentication and authorization.” With so many APIs, “it is easy to lose track of which API has which kind of authentication [and] authorization setup.” 

Beyond just access, Vegiraju also highlights the risk of “not properly validating your input parameters,” which can lead to severe vulnerabilities like SQL injection — especially “if you’re  inserting that content directly into a SQL statement.” It is therefore imperative to implement a standardized, rigorous API security framework that mandates consistent authentication, authorization and input validation for all APIs, regardless of their perceived criticality or development speed. 

This inconsistency otherwise becomes a breeding ground for exploitation. Venkata Naga Ravi Kiran Nizampatnam, senior network security engineer and cybersecurity researcher at Sprintpark, explains that a significant risk “lies in inconsistent security enforcement. Some APIs might be subjected to strong authentication, whereas in others, wide-open access might prevail.” He adds that another direct effect of sprawl is “the presence of stale or duplicate endpoints that attackers actively scan for. Such neglected and often-overlooked APIs become soft targets.” Organizations must establish a centralized API inventory and enforce consistent security policies across all endpoints to eliminate weak points and proactively decommission stale or duplicate APIs. 

The consequences of these ’soft targets’ are severe, frequently culminating in the exposure of sensitive data. A well-known incident illustrates this: A malicious actor abused an API without proper authorization checks to retrieve personal customer data of 37 million users — a reference to the 

T-Mobile data breach. Why did it happen? The API was publicly accessible and lacked proper rate limiting and authentication. Sometimes, even APIs not intended for public use become vulnerable if not properly managed. “If you don’t put [an API] behind an API gateway, all these are exposed to the public Internet,” cautions Agrawal. To mitigate this, all APIs — especially those with access to sensitive data — should be placed behind an API gateway with robust authentication, authorization and rate-limiting controls, even if not intended for public consumption. 

Nizampatnam recounts a similar scenario from one of his investigations, “During a breach I investigated, the zombie API had access to HR data inside. It had no logging and no rate limiting; the attackers used it to extract records at a very slow rate over several weeks and without being detected.” This silent exfiltration of data is a common outcome when APIs are forgotten or poorly secured. This highlights the necessity for continuous monitoring and comprehensive logging for all

APIs, including those believed to be deprecated, to detect anomalous behavior and prevent silent data exfiltration. 

“The overarching danger here is the potential to inadvertently expose PII through unmanaged or unseen APIs, coupled with an inability to respond quickly, as SecOps teams may lack clarity on how — or who — is responsible for fixing the problem,” says John Leon, VP of partnerships & business development at Apiiro. He adds, “it is clear that what you can’t see, you definitely can’t secure.” To address this, organizations must cultivate complete visibility into their API ecosystem and establish clear ownership and incident response protocols for all APIs, empowering SecOps teams to swiftly identify and remediate vulnerabilities and breaches. 

When API Sprawl Hits Home 

The fallout from unmanaged API sprawl does not stop at direct security vulnerabilities; it sends damaging ripples across critical business functions, particularly when it comes to regulatory compliance and the ability to respond effectively to incidents. Without a clear understanding of your APIs and the data they handle, meeting legal and regulatory requirements becomes nearly impossible.  

Agrawal of LambdaTest emphasizes how this lack of visibility directly undermines data protection efforts. For regulations like GDPR or CCPA, he points out that if an API isn’t properly documented or secured, fundamental principles are breached. “If we talk about GDPR, there is a principle of accountability. As a company, you violate that,” he explains. And this extends to requirements like data mapping and auditing. Ultimately, he reasons, “you cannot secure or comply with what you don’t know exists.” 

Vegiraju from Microsoft Azure Security echoes this concern, especially regarding how sprawl obscures data flow and handling. “With API sprawl, the main problem is because there are [so many] different APIs accessing the same data, you don’t know where the data is leaking from to the outside world.” This can lead to severe compliance breaches, as “API sprawl can lead to shadow or zombie APIs that handle sensitive data without oversight. For example, an outdated /v1/users endpoint may still expose full user profiles, including emails and phone numbers, without the knowledge of compliance or security teams.” 

And when a security incident does occur — perhaps exploiting one of these unknown or unmanaged APIs — the response is often hamstrung from the start. Leon of Apiiro highlights the impact on a critical metric: Mean time to remediation (MTTR). “A common KPI (and challenge) we see in many enterprise organizations is demonstrating a meaningful reduction in MTTR response rates,” he notes. The inability to reduce the time between identifying a high-business impact API risk at runtime and remediating it in code can have a direct and negative impact on the ability to deliver and maintain code in production. 

This delay in fixing problems is a direct consequence of the obscurity created by sprawl. Agrawal points out that during an incident, “because of API sprawl, you did not have proper documentation. You don’t know what all APIs have access to your database.” This crucial lack of information means your “time to mitigation will go drastically up and at the same time you’re also bleeding [data].” The minutes and hours lost trying to understand an undocumented API landscape are minutes and hours where an attacker can continue to cause damage, and the business impact mounts. 

AI Leads To Further API Problems 

If the current landscape of API sprawl already presents significant security and operational headaches, the rapid advancements in AI are poised to turn up the volume considerably. AI systems, by their very nature, often rely on a multitude of APIs for data ingestion, model interaction and exposing their own capabilities, leading to an even greater proliferation. 

Agrawal, speaking from his engineering experience at LambdaTest and leading the security efforts for Kane AI, a GenAI-Native testing agent for high-speed quality engineering, foresees a dramatic shift in scale and intricacy. AI is not just increasing the number of APIs — it is accelerating their creation beyond human oversight. API sprawl will not only grow in scale, but in complexity too, emphasizing that the adaptability of AI means many more complex integrations are on the horizon. This isn’t just about more of the same; it is about a fundamental change in how interconnected and rapidly evolving these API ecosystems will become. 

The speed at which AI can accelerate API creation is a key factor. Vegiraju observes, “One thing AI has done is that previously, you had to do at least a week’s effort to bring up an API. With AI, that time has drastically reduced to a couple of days or even a day.” While this acceleration can drive innovation, he asserts that “because the time has reduced, we should still not compromise on the quality.” 

And that is the crux of the issue. If organizations are already struggling with visibility, governance and security for their current API inventory, the AI-driven surge will only exacerbate these underlying problems. The pressure to innovate quickly with AI could easily lead to even more shadow APIs and a further dilution of security standards if not managed proactively. 

Getting a Grip on Your API Sprawl 

While the picture of API sprawl might seem daunting, the good news is that organizations are not powerless. By adopting a deliberate and multi-faceted approach, security leaders can start to untangle the web, reduce risk and regain control over their API landscape. The journey begins with one fundamental step: Seeing what’s actually there. 

• See What’s There 

You can’t secure what you don’t know exists — and this is the one thing all security experts agree on. The first step in managing API sprawl isn’t just discovery, it’s creating a single, unified system of record. 

“The first step is to document all of the APIs — to gather as much information as possible about every API available,” says Vegiraju. “There are cloud-native application platform tools that help you get this inventory and visibility.” Without a clear inventory, even the best security tools will fall short. A breach caused by an unknown or unmanaged API is not a matter of if, but when. “You have to maintain an inventory — and enforce it.” 

Agrawal reinforces this point, “API security is never the problem — it is always the discovery. Once you’ve discovered it, you’ll fix it.” But in large, dynamic environments, organizations need advanced automation that provides continuous visibility into how APIs behave across systems. At LambdaTest, he shares, “we use tools like eBPF at the kernel level to intercept network calls and maintain a dynamic inventory of our APIs.” 

The core recommendation here is to implement a living, centralized inventory — one that combines documentation, real-time discovery and regular validation. That’s the foundation for everything else: Governance, ownership and security. Without it, you’re flying blind. 

• Govern It and Own It 

Once you have visibility into your API assets, establishing governance and clear lines of ownership is critical. Without this, even a complete inventory quickly becomes outdated. Vegiraju emphasizes the need for formal oversight, “Basically, having a governing board is very important,” he explains. “If a team is taking a dependency on another team’s API, it should be properly documented, and that API must be approved by the board.” 

Part of governance is about accountability. “We have assigned ownership for all APIs,” says Agrawal. “We know exactly who owns which API.” This addresses the core issue with unchecked sprawl: “There ceases to be a single point of accountability.” 

But ownership must also support remediation. Leon of Apiiro explains one common challenge is “mapping a vulnerability identified by an API runtime solution back to the corresponding API in code, and then to the code owner responsible for fixing it.” There are more challenges, and to address them, organizations should establish a formal governance framework with a dedicated governing body and clear ownership for every API — ensuring documentation, approval and accountability throughout the lifecycle. 

• Embed Security and Act Decisively 

With discovery and governance in place, the next step is embedding security across the API lifecycle and acting decisively to manage sprawl. Vegiraju recommends a clear first move for chief information security officers (CISOs) handling unchecked API growth: “Start the deprecation process as soon as possible. And stop bringing up new APIs until you have defined a policy — that is very important. Stop the bleeding, then start making things better.” He urges leaders to challenge necessity, “Ask why. Why do we need these APIs? Are there no existing APIs that can serve the same use case? Only then move forward.” 

Agrawal advocates for more proactively hardening your security posture, “Apply zero trust to all APIs,” he advises, and integrate security directly into the development process through practices like “API security linting in CI/CD” and comprehensive governance covering “versioning, retirement, change and review.” But this shift also requires cultural change. The problem often lies in relegating security to an afterthought — “a big problem,” he says — advocating for empowering engineering and data science teams to build security-first mindsets from the ground up. 

Above all, organizations must adopt a “stop the bleeding” strategy by pausing new API deployments until clear security policies are in place, critically evaluating the necessity of every new API, embedding zero-trust principles and integrating security practices — such as linting and governance — throughout the lifecycle, while investing in ongoing education for all relevant teams. 

Secure Your APIs, Secure Your Future 

It is clear that API sprawl is a tangible security risk that quietly undermines businesses from the inside out. The tangled web of unknown, unmanaged and forgotten APIs creates a fertile ground for attackers, complicates compliance and can paralyze your response when things go wrong. But this challenge, though significant, is not insurmountable. 

The path to reclaiming control hinges on a commitment to visibility, robust governance and embedding security proactively throughout the entire API lifecycle. It is about moving from a reactive stance to a strategic approach. As Agrawal puts it, the future of API security is not just about better firewalls — it is about smarter governance, automation and visibility at scale. 

By embracing these principles, organizations can begin to transform their API landscapes from hidden liabilities into secure, strategic assets essential for innovation and future growth.