We are looking for a Senior Full-Stack .NET Developer to remediate security vulnerabilities, support legacy applications, and modernize services across .NET Framework and .NET 6/8+. You will work across backend, data, and frontend while partnering on secure delivery.

Responsibilities

- Investigate and remediate application security vulnerabilities across OWASP Top 10 and automated SAST/DAST findings
- Harden applications against SQL injection, XSS, and dependency-related risks
- Maintain and modernize legacy .NET Framework applications including ASP.NET Web Forms, ASP.NET MVC, WCF, and ASMX
- Build and enhance ASP.NET Core Web APIs and modern .NET services using clean architecture practices
- Implement secure data access with Microsoft SQL Server and ADO.NET
- Develop and refine frontend features using JavaScript and existing UI patterns
- Collaborate with DevOps to support secure CI/CD pipelines and production deployments
- Troubleshoot production issues and deliver timely fixes with minimal risk
- Review code changes for security, maintainability, and backward compatibility
- Document remediation decisions and modernization steps for future maintenance

Requirements

- 3+ years of full-stack .NET development experience
- Strong leadership and ownership skills to drive remediation and modernization work
- Daily availability aligned to 5:00 PM CT (Central Time)
- C# and .NET Framework expertise including ASP.NET MVC and Web Forms
- Strong application security knowledge covering OWASP Top 10 vulnerabilities




- REST API development skills with ASP.NET Core and modern .NET (6/8+)
- Microsoft SQL Server and ADO.NET skills for secure data access
- WCF experience supporting and maintaining legacy services
- JavaScript skills for frontend enhancements and integrations
- Strong troubleshooting skills to diagnose issues in large legacy codebases
- Clear communication skills to collaborate across engineering and DevOps
- Upper-Intermediate English skills (B2+)

Nice to have

- OAuth2 knowledge for secure authorization flows
- OpenID Connect knowledge for modern identity integration
- Octopus Deploy experience supporting deployments
- Strong HTML skills for maintaining legacy views
- Strong CSS skills for UI fixes and incremental improvements

We offer

- International projects with top brands
- Work with integral teams of highly skilled, diverse peers
- Healthcare benefits
- Employee financial programs
- Paid time off and sick leave
- Upskilling, reskilling and certification courses
- Unlimited access to the LinkedIn Learning library and 22,000+ courses
- Global career opportunities
- Volunteer and community involvement opportunities
- EPAM Employee Groups
- Award-winning culture recognized by Glassdoor, Newsweek and LinkedIn

EPAM is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, national origin, age, sexual orientation, gender identity or expression, disability, protected veteran status, or any other characteristic protected by applicable law.

📌 Senior Full-Stack .NET Developer (Colombia)
🏢 EPAM Systems
📍 Colombia