Application Penetration Tester

About OnDefend
OnDefend is a cybersecurity company focused on helping organizations identify, understand, and reduce risk through practical security testing, consulting, and technology-enabled services. Our work spans penetration testing, application and cloud security, red and purple team assessments, and continuous security validation.
Our team is distributed across the U.S., with headquarters in Jacksonville, Florida. We value people who take ownership, think creatively, communicate clearly, and continuously develop their tradecraft.
Job Overview
OnDefend is seeking an Application Penetration Tester who enjoys digging into applications, APIs, and supporting technologies to identify security weaknesses and help clients understand their risks. We are looking for a hands-on tester who brings curiosity, attention to detail, and a willingness to keep building their technical skills.
You will perform application security assessments using manual testing, source code review, and automated tools where appropriate. You will work within defined engagement scopes, collaborate with other testers, document reproducible findings, and communicate results clearly to the team and clients.
What You’ll Do
Execute penetration tests of web applications, APIs, backend services, and related technologies across diverse client environments.
Assess cloud environments for IAM weaknesses, service misconfigurations and privilege escalation paths, including where application flaws can be used to gain access to underlying cloud infrastructure
Work independently on assigned testing tasks and collaborate with other testers on larger or more complex engagements.
Test authentication, authorization, business logic, session management, input validation, and sensitive data handling.
Review application behavior, architecture, source code, and data flows to identify security vulnerabilities.
Use SAST, DAST, SCA, and other tools as appropriate, and manually investigate and validate potential findings.
Develop or adapt proof-of-concept scripts and lightweight tooling to demonstrate vulnerabilities when needed.
Validate findings, capture reproducible evidence, and prepare clear reports with practical remediation recommendations.
Maintain accurate testing notes and evidence, follow engagement scope and testing procedures, and communicate progress or blockers promptly.
Participate in peer review, share technical knowledge, and continue developing application security testing skills.
Work with engagement leads and other team members to clarify testing requirements, priorities, and technical questions.
What You Bring
3+ years of professional experience in application penetration testing, offensive security, or equivalent application security work.
Experience performing web application and API penetration tests within defined engagement scopes.
Hands-on manual testing experience with common vulnerabilities, including authentication and authorization flaws, IDOR/BOLA, injection, and business logic issues.
Working knowledge of HTTP, APIs, modern application architectures, and common application security weaknesses.
Proficiency with Burp Suite or comparable web security testing tools and ability to use or adapt proof-of-concept code.
Ability to read and understand source code in one or more languages such as Python, Java, JavaScript/TypeScript, Go, C#, or similar.
Familiarity with SAST, DAST, and SCA tools and an understanding of when manual validation is needed.
Clear technical writing, attention to detail, and the ability to document reproducible findings and collaborate with clients and teammates.
Preferred Qualifications
Experience testing cloud-hosted applications or services in AWS, Azure, or Google Cloud.
Experience with mobile applications, GraphQL APIs, microservices, serverless systems, or containerized environments.
Familiarity with cloud identity, service-to-service authorization, Docker, Kubernetes, or related technologies.
Experience with Semgrep or similar source-code analysis tools.
Relevant certifications such as OSCP/OSCP+, BSCP, GWAPT, GPEN, or similar.
Contributions to security research, CVEs, bug bounties, open-source projects, publications, or conferences.
Benefits at a Glance
Medical plan options, plus dental and vision coverage.
Short-term disability benefits.
401(k) retirement plan.
Employee Assistance Program (EAP) resources.
Benefit eligibility, plan options, and coverage terms are subject to applicable plan documents and company policies.
Applicants must be authorized to work in the United States. OnDefend does not sponsor, or take over sponsorship of, employment visas for this position, now or in the future.

Skills
Python, JavaScript, TypeScript, Java, C#, Golang, GraphQL

Experience
3+ yrs

Work arrangement
Yes