Senior Application Security Engineer

Apollo.io is the leading go-to-market solution for revenue teams, trusted by over 500,000 companies and millions of users globally, from rapidly growing startups to some of the world's largest enterprises.

Founded in 2015, the company is one of the fastest growing companies in SaaS, raising approximately $250 million to date and valued at $1.6 billion.

Apollo.io provides sales and marketing teams with easy access to verified contact data for over 210 million B2B contacts and 35 million companies worldwide, along with tools to engage and convert these contacts in one unified platform.

By helping revenue professionals find the most accurate contact information and automating the outreach process, Apollo.io turns prospects into customers.

Apollo raised a series D in 2023 and is backed by top-tier investors, including Sequoia Capital, Bain Capital Ventures, and more, and counts the former President and COO of Hubspot, JD Sherman, among its board members.

Role Overview

The Senior Application Security Engineer is a senior individual contributor responsible for strengthening Apollo’s secure software development lifecycle and reducing application risk across product, platform, and AI-powered features.

This role blends deep code-level application security work with strong cross-functional partnership. It includes application security reviews, threat modeling, AppSec tooling, findings triage and remediation follow-through, external testing intake, and developer enablement.

This role is calibrated at the L6 senior-IC level: owning semi-annual or annual goals, solving ambiguous problems with sound judgment, improving operational processes, and driving meaningful cross-team collaboration and influence.

Key Responsibilities

Secure SDLC, design review, and threat modeling

Own and continuously improve the secure software development lifecycle for Apollo applications so security is embedded into design, implementation, and deployment.

Perform application security reviews, threat modeling, and deep code-level analysis for high-impact product, platform, and AI features before launch.

Provide practical security architecture guidance to Engineering, Product, and IT teams

Help define and maintain application-security guardrails, secure design expectations, code review standards, and risk models for new and existing systems.

Vulnerability management and hands-on remediation

Drive execution-heavy vulnerability management across internal reviews, bug bounty, pentests, SCA/runtime findings, and other research signals, ensuring findings are validated, prioritized, routed clearly, and tracked through remediation and verification within SLAs.

Go beyond identifying issues: read the code, explain root cause, propose the safest fix, and directly implement or support remediation when needed for complex vulnerabilities.

Perform hands-on validation and offensive security testing of applications and fixes, including exploit development, bypass testing, adversarial thinking, and focused red-team-style exercises, to confirm remediations address the underlying issue rather than only the initial symptom.

Work across the kinds of application security issues common in modern SaaS environments, including authentication and authorization weaknesses, access control risks, OAuth and CSRF design flaws, SSRF, cryptographic and verification issues, information disclosure and data exposure risks, unsafe execution and deserialization patterns, and dependency or runtime vulnerabilities.

Apply clear, risk-based severity decisions using exploitability, data sensitivity, customer impact, and blast radius

Tooling, automation, and AI

Configure and improve AppSec tooling and integrations, including SAST configuration, ignore lists, dashboards, and other controls that maintain useful coverage without excessive noise.

Select, build, or refine security tooling, small automations, and workflow enrichments that reduce manual effort and scale AppSec operations responsibly.

Use AI to automate, transform, and scale security and engineering-adjacent processes where it materially improves speed, consistency, or signal quality, while still validating outputs with strong engineering judgment.

Embed AI-specific security checks into SSDLC reviews and code analysis, including input and output handling, AI-exposed APIs, prompt and response guardrails, and abuse or data-exfiltration paths.

Partner cross-functionally on AI security requirements and controls so AI systems and AI-powered features are designed, deployed, and operated securely.

Engineering enablement and partnership

Support and scale security enablement for engineers and security champions, including secure coding, AppSec, and AI-safety content.

Provide actionable remediation guidance, secure patterns, and examples that help engineering teams fix issues quickly and correctly.

Partner closely with Engineering, Product, Platform, Data, Legal, and other security teams to keep AppSec priorities aligned with business risk and product velocity.

Produce clear documentation, metrics, and written narratives that improve AppSec visibility, observability, and decision-making.

What Good Looks Like

Owns meaningful AppSec goals over a semi-annual or annual horizon and independently identifies the right solutions to ambiguous, open-ended problems.

Drives cross-team collaboration and operational improvements beyond isolated tickets or one-off reviews

Makes informed decisions by balancing technical detail, business context, customer trust, and long-term risk

Sets a high bar for ownership, communication, mentoring, and technical judgment, and helps raise the effectiveness of peers and partner teams.

Required Skills & Experience

5+ years of software engineering or application security experience, with meaningful hands-on AppSec depth in modern SaaS environments.

Strong software development skills and the ability to read, write, and ship production code; Ruby experience is highly valuable, and Python or similar scripting ability is a plus.

Strong Linux and cloud fundamentals, ideally with experience in GCP-backed environments.

Deep familiarity with common AppSec issues, secure design, secure authentication and authorization patterns, vulnerability management, and developer security tooling.

Demonstrated ability to perform deep code review, penetration testing, and exploit-oriented validation, and to either fix vulnerabilities directly or work closely with engineers to land durable remediations that hold up against bypass attempts and variant analysis.

Experience handling findings from bug bounty, pentests, internal reviews, or automated security tooling through closure and verification.

Experience using AI-assisted tools, automations, APIs, or structured workflows to improve engineering or security processes at scale.

Experience securing AI-powered systems or features, including AI API exposure, prompt and response handling, data protection, misuse scenarios, and monitoring expectations.

Strong written and verbal communication, stakeholder management, and influencing skills across technical and non-technical partners.