AppSec Engineer: Deterministic Testing & AI-SAST Expert

Crossing Hurdles; United Kingdom; On-site; GBP 70,000 - 110,000; Full time

Job summary

Crossing Hurdles is seeking an experienced security-focused engineer to design and implement application fixtures with embedded vulnerabilities or secure solutions, and to develop deterministic test cases and security-context manifests for AppSec assessments.

You will collaborate across teams to document technical insights, share findings, and iterate on pipeline improvements for realistic security evaluations, including agent-based architectures, while delivering actionable recommendations

Qualifications

• Has strong experience in application security, secure software development, or CyberSWE roles.
• Strong understanding of OSWE, LLM security, AI-powered static analysis (AI-SAST), and AppSec best practices.
• Proven track record designing or evaluating security architecture for traditional and agent-based applications.
• Expertise in building, securing, and testing application codebases, including identifying and remediating vulnerabilities.
• Exceptional written and verbal communication skills, focusing on precise technical documentation and collaborative feedback.
• Experience with synthetic security fixtures and deterministic testing approaches is highly desirable.
• Demonstrated ability to deliver thoughtful insights and actionable security recommendations remotely.

Responsibilities

• Design and implement application fixtures with embedded security vulnerabilities or secure solutions.
• Develop deterministic test cases and security-context manifests for application security assessment.
• Create detailed hidden answer keys for AI or scanner evaluation of code security.
• Evaluate and iterate on pipeline methodologies for realistic AppSec assessment.
• Document technical insights and methodologies with clarity in written feedback.
• Collaborate through clear communication to share findings and review peer contributions.
• Engage with agent-based security architecture and contribute to evaluation pipeline improvement.

Skills

Application security

Secure software development

OSWE

AI-SAST

AppSec best practices

Security architecture evaluation

Remote collaboration

Job description

Crossing Hurdles is seeking an experienced security-focused engineer to design and implement application fixtures with embedded vulnerabilities or secure solutions, and to develop deterministic test cases and security-context manifests for AppSec assessments.

You will collaborate across teams to document technical insights, share findings, and iterate on pipeline improvements for realistic security evaluations, including agent-based architectures, while delivering actionable recommendations