Capability Brief
Web Application and API Security Testing
We test web applications and their APIs the way attackers approach them - by examining every input, every authentication flow, and every assumption the application makes about its users.
What this is about
Where users, data, and business logic meet
Web applications sit at the intersection of users, data, and business logic. Whether it's a customer-facing SaaS platform, an internal admin interface, or a set of REST APIs powering a mobile app, these systems handle authentication, process sensitive data, and enforce access controls that determine who can see and do what. Casaba evaluates how these applications handle real-world attack scenarios, from credential stuffing to privilege escalation to business logic abuse.
What we test
Nine attack surfaces
Authentication and Session Management
Login flows, password reset mechanisms, token handling, MFA implementation and bypass scenarios, session timeout and invalidation, 2FA enrollment and synchronization issues.
Authorization Controls
Role-based access enforcement, privilege escalation between user roles, cross-tenant isolation in multi-tenant applications, admin interface access controls and RBAC implementation.
API Security
REST endpoint input validation, error handling and information disclosure, rate limiting on sensitive endpoints, API key scope and grant type enforcement, data ingestion endpoint security.
Client-Side Security
Cross-site scripting (XSS) in rendered user data, clickjacking and UI redressing, HTML injection through user-controlled fields.
Business Logic
Workflow bypass and repurposing of functionality, abuse scenarios like automated account creation, resource consumption attacks through expensive queries or large data requests.
Token Implementations
JWT signing and validation, claim manipulation and injection, cross-client token reuse, token scope enforcement.
Documentation Review
Developer documentation, API specifications, and onboarding guides reviewed for instructions that may expose security weaknesses or ask clients to share sensitive credentials like private keys.
Third-Party Dependencies and Components
Review of open-source libraries, frameworks, and packages used by the application for known vulnerabilities, outdated versions, and supply chain risks. Includes analysis of how the application manages and updates its dependency tree.
API Discovery and Attack Surface Mapping
Identifying undocumented endpoints, deprecated API versions still accessible in production, and shadow APIs that exist outside the organization's documented inventory. Testing starts with understanding the full surface before diving into individual endpoints.
How we approach it
Manual testing backed by targeted automation
Casaba uses a combination of manual testing and targeted automation. Testers work through the application as both authenticated and unauthenticated users, examining every input surface, API endpoint, and authentication flow. API endpoints are collected, profiled, and fuzzed using Burp Suite with targeted payload lists. Where source code is available, testing is augmented with code-informed analysis using tools like Semgrep to trace data flows and identify issues that dynamic testing alone would miss. SQL injection testing uses a combination of SQLmap and manual payloads, including specialized authentication bypass wordlists. We also review the application's third-party dependencies and component inventory for known vulnerabilities, and map the full API surface including undocumented and deprecated endpoints before beginning targeted testing.
Testing is informed by the OWASP Top 10, the CWE Top 25 Most Dangerous Software Weaknesses, and Casaba's own experience from over two decades of real-world engagements. We focus on the areas where automated scanners consistently fall short: authentication logic, authorization boundaries, multi-step workflows, and the subtle interactions between different components of a system.
What we find
Typical finding patterns
Authorization Bypass
Low-privileged users accessing administrative functions, other tenants' data, or performing actions outside their assigned role.
Remote Code Execution
Injection flaws in server-side input processing, deserialization, or template rendering that allow arbitrary code execution.
Cross-Tenant Data Access
Multi-tenant applications where isolation boundaries fail under manipulation, exposing one tenant's data to another.
Server-Side Injection
SQL injection, command injection, and other server-side injection vulnerabilities that enable data exfiltration or system compromise.
Authentication Bypass
Token manipulation, claim injection, or flaws in SSO and federated identity flows that let attackers impersonate other users.
Server-Side Request Forgery
SSRF enabling access to internal services, cloud metadata endpoints, or backend systems not intended to be reachable from the application layer.
Insecure Direct Object References
Attackers accessing or modifying other users' records by manipulating identifiers in API requests.
Stored Cross-Site Scripting
XSS in user-generated content that executes in the context of other users, including administrators.
Business Logic Flaws
Attackers bypassing payment flows, manipulating pricing, escalating access, or abusing workflows in ways the application designers did not anticipate.
Broken Access Control in APIs
API endpoints where client-side restrictions are the only enforcement and server-side authorization checks are missing or incomplete.
Vulnerable Third-Party Components
Open-source libraries and frameworks with known vulnerabilities running in production, often several versions behind available patches.
Excessive Data Exposure in API Responses
API endpoints returning more data than the client needs, exposing internal identifiers, user details, or system metadata that should be filtered before reaching the response. Also includes mass assignment vulnerabilities where attackers modify object properties like roles or pricing that should be read-only.
Unrestricted Resource Consumption
Missing rate limits, absent pagination controls, or batch request abuse that enables denial-of-service, data harvesting at scale, or resource exhaustion through computationally expensive operations.
Error Handling Weaknesses
Unhandled exceptions that expose internal state, fail open to bypass security controls, or create denial-of-service conditions. Applications that behave differently under error conditions than under normal operation, creating exploitable inconsistencies.
Why it matters
Automated scanners miss what matters most
A vulnerability in an API endpoint or authentication flow can expose customer data, enable account takeover, or allow unauthorized access to business operations. Automated scanning tools are good at finding known vulnerability patterns, but they consistently miss the logic-level issues that matter most: authorization boundaries that don't hold up under manipulation, authentication flows with subtle timing or response differences, and business logic that can be repurposed by a determined attacker. Regular, hands-on testing by experienced consultants is how these issues get found.
Need your systems tested?
We've been testing web applications and APIs for over two decades. Let's talk about yours.
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