Protect and Safeguard API Keys from Leakage and Misuse

A skeleton key is an interesting concept. The ability to unlock all the rooms of a house with one simple tool is incredibly useful when in the right hands - the homeowner, for instance. But when locked in a mischievous grasp, this tool quickly becomes a curse for the homeowner. No secret is safe; everything is laid bare for malicious wielders to use for their (often) malignant desires.

When developing the API keys of their applications, mobile developers can learn from the cautionary tale of a skeleton key wielded by deceitful hands. Authorized API keys grant access to a variety of functionalities and endpoints with a single API, much like a skeleton key grants access to various physical points of entry. While there are important differences (a physical vs digital key) the point remains - both keys can be incredibly useful or harmful, depending on the user’s intent.

Safeguarding critical API keys is paramount to mobile application security. We’ll dive deep into the harms that stem from API key leakages, best practices to avoid breaches and misuse, and how to apply these methods to your mobile app protection strategy.

What are API keys?

API keys are a critical component in the development of today’s applications. In literal terms, an API key is a unique code that authenticates and authorizes access to one or more APIs. Essentially, it can be thought of as a password an application uses to authorize itself as genuine when contacting the API provider. This ensures only verified applications are authorized to gain access to datasets or certain functionalities.

The primary functions of API keys are three fold: authentication, authorization, and usage tracking. First, as mentioned earlier, API keys authenticate the identity of an application or its user that is submitting an API request. This assists in verifying the application is genuine and not a malicious clone. Second, the API key determines which resources or level of functionality are allowed to access the API. For example, whether a user is requesting access to premium content on a streaming application that’s unavailable on their current plan. Lastly, developers and security teams leverage API keys to monitor app usage, administer rate limits, and evaluate app performance.

These are vital functions to optimizing and maintaining a secure user experience. As a consequence, API keys are highly valuable and need to be protected from attackers. The harm that results from API key misuse can be devastating.

What causes an API key leak or breach

API keys can be leaked in different ways. When they are leaked, it can often be due to human error. Below are a few of the more common means.

Hardcoded API keys

Developers may make the mistake of hardcoding API keys directly into their code. If the code is publicly shared or unauthorized personnel perform static analysis, these keys have high potential to be exposed. Back in 2018, Twitter had a famous API key leak that affected thousands of mobile apps. A developer erroneously committed a file that had the API key to a GitHub repository, which made the Twitter API key publicly accessible.

Server misconfiguration

In some cases, servers can be misconfigured in a way that exposes API keys in error messages or logs. If someone were to access these logs, the API keys would be visible. Thus, it’s essential to practice secure logging and protect the server-side of your application.

Accidental key sharing

As stated, human error is the cause for most API key leaks. Developers may share API keys via communication channels such as Slack, email, or other methods. It could be as simple as taking a screenshot of a config file that unknowingly exposes an API key. Teams must stay vigilant about communicating securely within their organization.

The harms of API key exposure and abuse

Mobile applications harbor significant amounts of sensitive financial, medical, and PII (personally identifiable information) data. Thus, they’re prime targets for attackers that wish to gain access to valuable data. Focusing on the API keys within a mobile application allows bad actors to streamline their efforts by gaining access to multiple resources or functions within an application at once. Damage can be swift and ferocious if proper protections aren’t in place. Below are a few examples of the categories of fallout when API keys are leaked.

Data breaches

Mobile apps are currently under siege. A recent Enterprise Strategy Group survey found 62 percent of organizations have faced at least one mobile app security incident over the past year. 92 percent of those same organizations faced multiple incidents, averaging 9 incidents per organization. After malware attacks, the most common type of experienced incident was a data breach or leak, which was answered by 45 percent of respondents.

When a breach does occur, the effects can be devastating. Attackers obtain these API keys to access sensitive data that’s stored either in databases or other systems for nefarious purposes. Not only does this lead to significant damage to brand reputation, but it opens the door to privacy violations and legal consequences.

Research conducted by the security firm CloudSEK discovered hundreds of apps using the Razorpay API to facilitate mobile payments unintentionally exposed the API key. Among these were multiple large apps with millions of users. The developer error could cost the apps and their users dearly, as financial information was made readily available for hackers to profit from.

Financial loss (including compliance violations)

In 2025, the average cost of a mobile application security incident ranges from just under a million up to several million dollars. Loss in this instance refers to a number of factors. Some notable examples are fraud, theft, revenue churn, legal recourse, ransom payments, and fines in relation to compliance violations. API leaks can lead to compliance violations with specific regulations like HIPAA and GDPR, which can result in millions of dollars in fines. The impact to an app publisher’s brand can be equally damaging.

Brand damage

Consumers place a substantial amount of trust in their mobile applications. Their personal data and financial information are present on a variety of mobile apps, from their bank to an ecommerce platform. Apps in violation of this trust place themselves at risk of losing the confidence of current and potential customers.

Unauthorized access that disrupts operations

We’ve established that API keys in mischievous hands can be extremely damaging. Not just to users, but to the app developers themselves. Leaked API keys can result in threat actors consuming third party APIs your app relies on. The actors can consume the third party APIs to a point that exceeds rate limiting or thresholds your app would normally abide by. This can result in a disruption of access to the API by other legitimate users of your app.

Account takeovers

Compromised API keys may lead to bad actors gaining access to takeover user accounts to conduct fraudulent activities. They may initiate fraudulent transactions, intimidate users into coercion, modify personal information, or send messages impersonating the user.

Top 5 methods to safeguard API keys against leakage and misuse

Fortunately, there are protection mechanisms and recommended best practices to minimize risks against API leaks and abuse. To avoid the harms we mentioned earlier, it’s essential mobile app developers embody the five strategies below during mobile app development.

1. Avoid client-side API key exposure

   A common and dangerous mistake is hardcoding API keys into an application’s source code. This is a huge no-no in the world of secure mobile app development. Hardcoding API keys simplifies the attacker’s mission by making API keys readily accessible to anyone that downloads the application and employs static analysis.

   Ensuring API keys are not included in publicly available config files also avoids client-side key exposure. If keys are stored in code repositories or a part of an app bundle, sensitive information has the potential to be exposed. Therefore, it’s best to keep API keys on the server-side, away from public eyes. This is especially true for API keys that demand higher security levels and control. Storing the keys in a secure server and having the server deal with the API requests on the application’s behalf provides an additional layer of security.

2. Secure API key storage

   Securely storing API keys is also critical to maintaining a secure application. Leveraging environment variables set on the device OS or the app’s server separates the API keys from the codebase. Not hardcoding the API keys into the codebase creates easier configurations for different environments as well, like development, staging, and production. If the API keys are stored on the device or a database, encryption is another key method to deter unauthorized access.

   To further increase secure API key storage, teams can use dedicated API secrets management tools, like AWS Secrets Manager. Systems like AWS Secrets Manager supply encrypted key storage, access control, and more.

3. Implement API key restrictions

   Restricting access to API keys is one of the best ways to prevent unauthorized access. Development teams can add API key restrictions based on specific factors like IP addresses and referrer URLs. Without satisfying these requirements, these API keys are inaccessible, even if the API key is leaked. To strengthen these restrictions, organizations should also apply the principle of least privilege. Each API key should only have the minimum necessary permissions to fulfill its purpose, again minimizing the impact of a leakage or breach.

4. Monitor and manage API keys in real time

   Proactive management of API keys adds yet another layer of security to mobile applications. An example of proactive API key management is regular rotation of API keys. Development teams should regularly create new API keys then update their app to accept them and deactivate the old keys. Hackers are left a few steps behind and the chances of an event are further reduced.

   Proactive management is great, but development and security teams need a strategy in the event of a leakage or breach. Teams should identify which usage patterns would indicate a breach or API abuse. Monitoring API usage and setting up real-time notifications for suspicious activity assists teams to stay on top of unauthorized API key access.

5. Employ secure development practices

   Security is no longer an afterthought in the development lifecycle. Rather, teams need to incorporate mobile app security throughout each stage to thwart the threats facing them today. Thus, when developing API keys, development teams need to practice secure development standards to prevent costly leaks or harm down the road.

   The primary step in API development is evangelizing the importance of secure development practices within your organization. Your team needs to fully understand the harms of irresponsible development. They also must be made aware of the risks that are out there, the attack methods used, and best practices to avoid API key leaks or breaches.

   The next step towards secure API key development is verifying that all API requests are made over HTTPS. Establishing secure API communication that encrypts data while in transit prevents hackers from executing man-in-the-middle attacks.

   We mentioned earlier that API keys should be stored separate from code repositories. Regularly scanning your code repositories for API keys and secrets serves as an extra check against costly mistakes.

   Finally, regular mobile application security testing and penetration testing are a litmus test for your application before releasing into production. Following guidelines like the OWASP Top 10 for Mobile and API security risks is a great starting point to identify and fix app vulnerabilities, including API keys.

A multi-layered strategy for powerful mobile API security

Protecting and safeguarding API keys should be a part of a larger mobile application security strategy. Incorporating multiple layers of security significantly increases your security posture and minimizes the risk of a security incident or breach, including API keys. Guardsquare’s mobile app security solutions employ various techniques, including polymorphic protection, to dramatically increase the difficulty for bad actors to steal API keys or attack your application.

Implement code obfuscation

Attackers will pour over function, class, and variable names to find clues to obtaining critical information within an application. Similar to encryption, DexGuard and iXGuard morphs these names into meaningless character sequences. Again, it becomes significantly more difficult for bad actors to understand the application’s logic in order to locate where API keys and sensitive data is within the app.

Amending the flow of the code’s logic makes it nigh impossible for reverse engineers to determine the execution path of an application, much less know how API keys are used or protected. DexGuard and iXGuard achieves this by implementing artificial code loops, branches, and jumps to throw the scent off from a would-be attacker.

Integrate mobile app security testing into your CI/CD workflow

Performing regular security tests and pentests against your application is an excellent preventive measure to identify exposed API keys before publishing the latest version of your app. Integrating security testing into your CI/CD workflow with an application like AppSweep will identify common vulnerabilities and risks to correct before app publication. These include hardcoded API keys and secrets, insecure key storage, and flaws in your app’s logic that could be taken advantage of. AppSweep won’t just identify the risks, however. In conjunction with identification, the solution provides actionable recommendations for you to take to correct vulnerabilities and protect your API keys from potential harm.

Apply Runtime Application Self-Protection (RASP) checks

Protecting against tampering like man-in-the-middle attacks is a critical layer in your mobile application security strategy. Preventing mobile app tampering avoids situations where someone can manipulate the behavior of your app to make authenticated calls into your APIs, but with tampered inputs or outputs.

DexGuard and iXGuard automatically inject runtime checks to detect if an attacker attempts to debug, tamper, or hook into an application at runtime. These checks are obfuscated as well to protect them from dynamic analysis. The checks can also be programmed to take subsequent actions when certain activities are detected. For instance, an app may be auto-programmed to crash when a potential man-in-the-middle attack is detected.

Environment checks

Attackers often attempt to gain access into mobile applications by running them in insecure environments. Similar to the anti-tampering and anti-debugging checks mentioned above, there are runtime checks that can be performed to detect the state of the environment an application is running in. The checks identify if the app is running in an insecure environment, like running on an emulator, operating in a virtual environment, or a debugger is present. Just like the anti-tampering checks, once a corrupt environment is detected, the app can take predetermined actions to thwart the threat, like crashing the application. Using strong detections for these scenarios, like limiting access to a debugger, can help prevent dynamic attacks that seek to uncover or expose sensitive API key information.

Server-side validation with mobile application attestation

Client-side integrity and protection is vital to application security. However, server-side protection is equally important, especially when it comes to API security. Proactive measures like mobile app attestation ensures you verify the authenticity and integrity of the application that is interacting with your APIs.

App attestation from Guardsquare is built on flexible and configurable server-side security policies. The security policies contain specific criteria that apps and devices must meet before access is granted to them. It extends the reach of your client-side protections with custom policies based on aggregated threat monitoring data. Adding this layer of protection to your real-time threat monitoring capabilities ensures only legitimate applications interact with your APIs at runtime - decreasing the chances of leaks leading to API abuse.

Exercise responsible API key management

There are substantial risks to hardcoding API keys into your codebase. Guardsquare does encrypt these API keys, but it’s best to avoid embedding them into your codebase altogether. DexGuard and iXGuard will reduce the risk of unwanted key exposure, but a robust security strategy would dynamically call your API keys from secure backend services whenever possible.

Limiting the servers your mobile application interacts with provides another measure to increase your security posture. SSL pinning verifies that the mobile app only communicates with predefined backend servers. It provides yet another measure against attackers intercepting API requests through man-in-the-middle attacks, among other means.

Conclusion

Minimizing risks to API keys by embracing enhanced security protections is a step all mobile app developers should take in today’s climate. The harms of a leak or breach event are too great to leave to chance. Following API security best practices and reinforcing your security posture with methods like obfuscation and code hardening, RASP protections, and app attestation will minimize the risk of an event and maintain application integrity. Learn more about how Guardsquare can protect and safeguard your application, including your API keys, today.