API security vulnerabilities are becoming an identity governance problem

At a glance

What this is: This is an analysis of why API security vulnerabilities are increasingly governed as an identity and access problem, with weak credentials, token handling, and third-party integrations driving exposure.

Why it matters: It matters because IAM, PAM, and NHI programmes now have to govern API trust boundaries, token binding, and integration scope as first-class security controls.

By the numbers:

• 92% of organizations using APIs suffered a breach within the last 12 months.
• 84% of security professionals experienced an API security incident in the past year.
• API-related vulnerabilities are now costing organizations up to $87 billion annually.
• Only 27% of organizations have a full API inventory and know which APIs exchange sensitive data.

👉 Read Raidiam's analysis of API security vulnerabilities and mitigation

Context

API security vulnerabilities are weaknesses in authentication, token handling, transport security, integration boundaries, or business logic that let an attacker misuse an API. In practice, the problem is not just code quality. It is that many organisations still treat APIs as technical plumbing rather than governed identity pathways, even though they move sensitive data and authorize machine-to-machine access.

The article argues that bearer-token dependence, limited API visibility, and weak third-party control create conditions where compromise becomes easier and harder to detect. That makes API security a direct concern for NHI governance, workload identity, and access control design, especially where APIs sit behind services, partners, and automation layers. Raidiam’s starting point is typical for enterprises that have scaled APIs faster than their governance model.

Modern API ecosystems also shift risk away from single sign-on and user-facing controls toward credential binding, transport trust, and policy enforcement at the resource server. Where those controls are weak, attackers do not need to defeat the whole environment. They only need one exposed token, one over-trusted integration, or one poorly governed API path.

Key questions

Q: What breaks when API security relies on bearer tokens alone?

A: Bearer-only API security breaks when a token can be intercepted and replayed by anyone who possesses it. That means the token no longer proves the sender’s identity, only possession. In practice, this increases the value of logs, proxies, and compromised endpoints as replay sources, and it makes token binding or sender-constrained designs much more important for high-risk APIs.

Q: Why do APIs with weak visibility create governance risk?

A: Weak visibility creates governance risk because teams cannot enforce access policy on endpoints they have not inventoried. When APIs are unknown, shadowed, or misclassified, access reviews miss them, monitoring is incomplete, and offboarding does not reach every trust path. That turns API sprawl into an identity control problem, not just an operations problem.

Q: What do security teams get wrong about third-party API risk?

A: They often focus on the vendor connection itself and miss the lifecycle of the entitlement behind it. If a partner API remains active after scope changes, contract changes, or ownership changes, the access path stays valid even when the business need no longer exists. Governance has to follow the relationship all the way to revocation.

Q: How should organizations reduce token replay risk in APIs?

A: Organizations should reduce replay risk by binding tokens to a specific client, limiting token lifespan, and enforcing stronger transport trust on high-value endpoints. The goal is to make a stolen token less useful outside its original session and sender context. That approach works best when paired with complete inventory and tighter control over partner integrations.

Technical breakdown

Bearer tokens and why interception still works

Bearer tokens remain dangerous because possession often equals authorization. If a token can be replayed after interception, the attacker does not need the original user or service account password. This is why token theft, proxy abuse, and session replay remain practical attack paths in API ecosystems that rely on simple presentation-based authorization. Certificate binding changes that model by tying token use to a specific client certificate, which reduces the value of intercepted credentials. The underlying problem is not token format alone, but whether the token is bound to a verifiable sender at runtime.

Practical implication: move high-value APIs away from bearer-only trust and require sender-constrained authentication where feasible.

API discovery and visibility gaps

You cannot govern what you cannot inventory. API sprawl creates blind spots across internal, partner, and shadow endpoints, especially when teams deploy services independently and reuse credentials across environments. Visibility matters because the security model differs for public APIs, internal service APIs, and third-party integrations, yet many organisations lack a complete map of which APIs exist and which ones exchange sensitive data. Without that inventory, access review, monitoring, and incident response all start late. The control failure is not just discovery itself, but the absence of authoritative ownership and lifecycle oversight for each API path.

Practical implication: build a complete API inventory tied to ownership, data sensitivity, and authentication method before tightening policy.

Third-party integrations and business logic abuse

Third-party APIs increase dependency risk because one organisation’s trust decision becomes another organisation’s attack surface. Even when credentials are valid, business logic can still be abused if the API permits actions that are inconsistent with intended workflow, transaction limits, or partner scope. That makes supply chain exposure and logic abuse different from simple credential theft. The challenge is governance: who approved the integration, what data it can reach, what actions it can trigger, and how quickly access is removed when the relationship changes. Strong API security therefore requires both technical controls and lifecycle discipline around partner access.

Practical implication: enforce scoped partner entitlements, short review cycles, and offboarding controls for every third-party API relationship.

Threat narrative

Attacker objective: The attacker aims to impersonate trusted API traffic, extract data, and manipulate application workflows through authorized channels.

1. Entry occurs when an attacker intercepts a bearer token, abuses weak credentials, or exploits a poorly protected third-party API connection.
2. Escalation follows when the token or integration is replayed against protected resources, allowing unauthorized actions and data access without further authentication.
3. Impact arrives through data exposure, business logic abuse, or broader service disruption once trusted API pathways are used at scale.

Breaches seen in the wild

• Shai Hulud npm malware campaign — Shai Hulud campaign: npm malware exposed secrets on GitHub.
• Salesloft OAuth token breach — hackers stole OAuth tokens to access Salesforce data via Salesloft.

Read our 52 NHI Breaches Analysis report for a comprehensive view of breaches impacting Non-Human Identities including AI Agents.

NHI Mgmt Group analysis

API security is now an identity governance problem, not a perimeter problem. The article’s focus on bearer tokens, mTLS, and non-shareable credentials shows that the real question is who or what is allowed to act on behalf of whom. When API traffic carries identity decisions, access control has to move from static authentication to governed trust relationships. Practitioners should treat every API as an identity boundary with its own lifecycle, ownership, and review cadence.

Bearer-token trust is a weak assumption because possession-based access is too easy to replay. That model was designed for simpler integration patterns where presentation of a token was enough to establish trust. It fails when tokens can be intercepted, reused, or forwarded across services without sender verification. The implication is that API governance cannot rely on token existence alone as evidence of legitimate access.

API inventory drift: when organisations cannot identify which APIs exchange sensitive data, they cannot govern risk at the point of use. This is more than a discovery gap. It means access review, monitoring, and incident response are all operating on incomplete scope, which leaves partner APIs and internal endpoints outside normal controls. Practitioners should treat inventory completeness as a prerequisite for meaningful identity governance.

Third-party API access expands the blast radius of one poor trust decision across multiple organisations. The article correctly points to supply chain risk, but the deeper governance issue is delegated trust without tight lifecycle control. If a partner relationship changes and access is not revoked, the API remains authoritative long after the business relationship has shifted. Practitioners should align partner offboarding with entitlement removal, not just contract closure.

mTLS and certificate-bound access tokens shift the control problem from token possession to cryptographic sender proof. That matters because API abuse often succeeds when a stolen token is accepted anywhere it is presented. Sender-constrained design narrows replay opportunities and reduces the value of intercepted credentials. Practitioners should evaluate whether high-risk APIs justify stronger sender binding, particularly where data sensitivity or partner access increases the attack value of a single token.

From our research:

• 72% of organisations have experienced or suspect they have experienced a breach of non-human identities, according to The 2024 ESG Report: Managing Non-Human Identities.
• A separate finding from the same report shows that enterprises that have experienced a compromised NHI averaged 2.7 separate incidents in the past 12 months.
• For deeper context on identity governance gaps, see the Ultimate Guide to NHIs , Key Challenges and Risks for the visibility and privilege issues that often underpin API exposure.

What this signals

API governance is converging with NHI governance. Once APIs become the mechanism through which services, partners, and automated workloads act, the programme has to manage credentials, trust binding, and entitlement lifecycle together. That is why API security work increasingly belongs alongside identity governance rather than sitting only with application teams.

The practical signal for practitioners is that discovery, ownership, and sender-constrained authentication now need to be measured together. With 72% of organisations already experiencing or suspecting an NHI breach in our research, the boundary between workload identity and API security is no longer theoretical. Teams that cannot map their APIs cannot reliably govern their identities.

Identity blast radius: the real risk is not one bad token but the number of systems that trust it. When partner APIs, internal services, and automation layers all accept similar credentials, a single exposure can cascade across environments. Practitioners should narrow trust domains, shorten review cycles, and use internal controls that make replay and reuse harder at each hop.

For practitioners

• Inventory every API and tie it to an owner Map public, internal, and partner APIs to business owner, data sensitivity, authentication method, and dependency chain. Without that inventory, review and monitoring will miss the endpoints that matter most.
• Replace bearer-only trust on high-value APIs Prioritise certificate-bound tokens or other sender-constrained patterns for APIs that expose sensitive data or payment workflows. This reduces replay value if tokens are intercepted in transit or from logs.
• Treat partner access as lifecycle-managed entitlement Define onboarding, review, and offboarding for every third-party integration, and revoke credentials when the relationship or scope changes. Contract closure without entitlement removal leaves residual access in place.
• Test for business logic abuse, not just authentication failure Add abuse cases to API security testing that attempt over-limit transactions, unauthorized workflow chaining, and scope escalation through valid credentials. Valid authentication does not mean valid intent.

Key takeaways

• API security vulnerabilities have become identity governance failures because tokens, integrations, and trust decisions now carry machine access.
• The article’s own data shows the scale of the problem, with 92% of API-using organisations reporting a breach in the last 12 months and visibility still lagging.
• Practitioners should focus on inventory, sender-constrained authentication, and partner lifecycle controls before adding more monitoring noise.

Key terms

• Bearer Token: A bearer token is an access credential that grants authorization to whoever presents it. In API environments, that convenience becomes a risk because interception or replay can turn possession into unauthorized access unless the token is bound to a sender or tightly constrained.
• Certificate-bound Access Token: A certificate-bound access token is linked cryptographically to a specific client certificate so it cannot be reused freely elsewhere. This reduces replay value and strengthens sender proof in API authentication, especially where high-value services or partner integrations make intercepted tokens attractive targets.
• API Inventory: An API inventory is the authoritative record of what interfaces exist, who owns them, what data they touch, and how they are authenticated. For identity governance, it is the baseline control that makes review, monitoring, offboarding, and risk prioritisation possible across distributed services.
• Business Logic Abuse: Business logic abuse occurs when an attacker uses a valid API in a way the application designer did not intend, such as exceeding limits, chaining actions, or misusing workflow assumptions. The API is functioning technically, but governance and policy are failing at the intent layer.

Deepen your knowledge

NHI governance, agentic AI identity, and machine identity lifecycle are core topics in our NHI Foundation Level course, the industry's only accredited NHI security programme. If you are responsible for identity security strategy or NHI governance in your organisation, it is worth exploring.

This post draws on content published by Raidiam: Why API Security Vulnerabilities Should Keep You Up at Night. Read the original.