9 Common API Vulnerabilities That Lead to Data Breaches

9 Common API Vulnerabilities That Lead to Data Breaches

What Are the Common API Vulnerabilities That Lead to Data Breaches?

Common API vulnerabilities include broken authentication, broken object level authorization, excessive data exposure, injection attacks, security misconfiguration, lack of rate limiting, improper asset management, weak encryption, and insufficient logging. These flaws allow attackers to access sensitive data and disrupt business operations.

APIs are the connectors that allow software applications to communicate with each other. When these connectors carry security flaws, attackers can break in and access customer data, payment records, and private business information. According to Salt Security, 99% of organizations faced API security issues in the past year, and API vulnerability exploitation grew 181% in 2025.

Understanding these common API vulnerabilities is essential for anyone building or managing modern software. Each weakness creates a different path for attackers to reach your data. The global average cost of a data breach reached $4.44 million in 2025, and a growing share of those breaches started through unprotected API endpoints.

• 99% of organizations: faced API security problems in the past year
• 181% growth: in API vulnerability exploitation during 2025
• $4.44 million: global average cost of a data breach in 2025

1. Broken Authentication in APIs

Weak authentication allows attackers to access APIs without proper identity verification. When an API does not check user credentials correctly, anyone can impersonate legitimate users and reach protected data.

Salt Security found that 41% of production APIs carry authentication problems. Attackers exploit weak tokens, stolen session cookies, or missing multi factor checks to hijack accounts. The financial impact is severe because every compromised session can unlock customer records, payment methods, and internal systems.

• 41% of APIs: have authentication flaws in production environments
• Stolen tokens: let attackers bypass login screens entirely
• Session hijacking: gives full access to user accounts and data

2. Broken Object Level Authorization (BOLA)

BOLA lets attackers access data belonging to other users by simply changing an object ID in an API request. This is the number one API security risk on the OWASP list and accounts for roughly 40% of all API attacks.

For example, a banking API that returns account details using a URL like /api/account/12345 can be exploited if the server does not verify that the requesting user owns account 12345. An attacker can swap the number and view any customer data. Parler suffered a massive breach in 2021 when BOLA flaws exposed 70TB of user data including posts, images, and videos.

• 40% of all API attacks: involve broken object level authorization
• 70TB of data exposed: in the Parler BOLA breach of 2021
• Simple ID manipulation: is all an attacker needs to exploit this flaw

3. Excessive Data Exposure

APIs expose more data than necessary in their responses. When an API returns entire user profiles instead of just the fields needed, it leaks sensitive information that should stay private.

Salt Security reports that 44% of organizations discovered sensitive data exposure through their APIs in the past year. This happens because developers often return full database records without filtering out fields like Social Security numbers, home addresses, or internal notes. Even well intentioned APIs can expose too much when response schemas are not carefully designed.

• 44% of organizations: found sensitive data exposure in their APIs
• Full record returns: leak private fields that users never see in the app
• Poor response filtering: is the root cause in most cases

4. Injection Attacks on APIs

Attackers inject malicious commands into API requests to trick the server into executing unwanted actions. SQL injection and command injection are the most common forms, and they can lead to full database compromise.

Akamai reports that SQL injection remains one of the top attack vectors targeting APIs. When an API accepts user input and passes it directly to a database without proper sanitization, an attacker can insert SQL commands that read, modify, or delete records. Traceable found that injection attacks contributed to a significant share of API breaches in 2025, making input validation a critical defense.

• SQL injection: remains a leading API attack method worldwide
• Input sanitization: is missing in many API endpoints
• Database compromise: can result from a single injected command

5. Security Misconfiguration

Improper API settings create exploitable weaknesses. Default credentials, open cloud storage buckets, and debug mode left running in production are all examples of misconfigurations that attackers actively scan for.

Research shows over 90% of web applications contain some form of security misconfiguration. For APIs, the most dangerous mistakes include leaving administrative endpoints open to the public, using default API keys, and failing to disable detailed error messages that reveal internal system details. Traceable reports that DDoS and fraud are the most frequent methods used to breach APIs, accounting for 37% and 31% of incidents respectively.

• Over 90% of apps: contain at least one security misconfiguration
• Default credentials: are the first thing attackers try
• Debug mode in production: exposes internal server details to attackers

6. Lack of Rate Limiting

Without request limits, attackers can flood APIs with thousands of calls per second. This enables brute force attacks, credential stuffing, and denial of service attacks that take the entire service offline.

Rate limiting restricts how many requests a single user or IP address can make within a time window. APIs without this protection are sitting ducks for automated attack tools. Traceable found that brute force attacks moved into the top three API attack methods in 2025, showing that attackers are actively exploiting unprotected endpoints at scale. Only 21% of organizations report a high ability to detect attacks at the API layer.

• Brute force attacks: entered the top three API attack methods in 2025
• Only 21% of companies: can detect attacks effectively at the API layer
• No rate limits: means attackers can try every password combination instantly

7. Improper Asset Management

Old or undocumented APIs remain exposed and unsecured when teams lose track of them. These shadow APIs carry known vulnerabilities that nobody monitors or patches.

Indusface reports that over 40% of organizations lack full visibility into their API attack surface. When development teams build test endpoints, deprecated services, or third party integrations without proper documentation, these shadow APIs become hidden entry points for attackers. The median time to exploit a known vulnerability is now under 5 days, while the average time to remediate exceeds 60 days, creating a massive window of exposure.

• Over 40% of organizations: lack visibility into their full API inventory
• Shadow APIs: are undocumented endpoints that nobody monitors
• 55 day gap: between vulnerability discovery and average patch time

8. Weak Encryption and Data Protection

Poor encryption exposes sensitive data during transmission and at rest. APIs that use outdated TLS versions or transmit data without encryption give attackers an open channel to intercept information.

CrowdStrike notes that encrypting API traffic with HTTPS and TLS is a fundamental security requirement, yet many APIs still accept unencrypted connections or support weak cipher suites. When data travels without encryption, attackers on the same network can capture login credentials, personal information, and payment details. This vulnerability is especially dangerous for mobile APIs that connect over public WiFi networks.

• Outdated TLS versions: leave API traffic open to interception
• Unencrypted endpoints: expose data to anyone on the same network
• Mobile APIs: are especially vulnerable on public WiFi

9. Insufficient Logging and Monitoring

Lack of monitoring delays detection of API attacks. Without proper logging, security teams have no visibility into what is happening on their API endpoints and cannot respond to breaches quickly.

Breach data shows that attacks detected within 200 days cost an average of $3.87 million, while those exceeding 200 days cost $5.01 million. The average breach lifecycle is 258 days, giving attackers more than eight months to move through systems and steal data. Only 21% of organizations have strong API attack detection capabilities, meaning the vast majority of breaches go unnoticed until external parties report them.

• $1.14 million difference: between early and late breach detection costs
• 258 day average: time from breach start to full containment
• Only 21% of organizations: can detect API attacks effectively

Key Takeaways

• Common API vulnerabilities caused 57% of organizations to suffer at least one data breach in the past two years
• BOLA is the number one API risk, responsible for 40% of all API attacks globally
• Broken authentication affects 41% of production APIs and enables account takeover
• Over 40% of organizations cannot see their full API attack surface, leaving shadow APIs exposed
• Early breach detection saves over $1 million compared to late discovery
• API security is now a core skill requirement for any cloud security engineer
• Regular API audits, strong encryption, and continuous monitoring are the best defenses