Mia Castellanos Application Security Engineer
San Francisco, CA • appsec@gmail.com • +1 415-555-0184
Profile Summary
- Application Security Engineer with 9 years of experience hardening consumer SaaS platforms across consumer cloud storage, collaboration, and content platforms, specializing in secure code review, threat modeling, and developer enablement.
- Solid technical background across review languages (Java, Python), SAST (Semgrep, SonarQube), DAST (Burp Suite, OWASP ZAP), SCA (Snyk, Dependabot), and security frameworks (OWASP ASVS), with strong fundamentals in secure-by-default design, automated triage, and developer enablement.
- Deep expertise in secure SDLC and shift-left practices, threat modeling and secure design review, SAST, DAST, and SCA triage, and API and microservices security, applying practices such as OWASP ASVS-driven control mapping and security champions enablement to deliver secure, audit-ready, and developer-friendly software.
- Engaged collaborator working cross-functionally with Engineering, Product, and Platform Security leadership in DevSecOps-first engineering organizations, contributing to design reviews, sprint planning, and post-incident retrospectives with a pragmatic, ownership-first mindset.
- Senior practitioner who shares technical excellence and fosters a culture of low-friction security and paved-road tooling through pattern authoring and design coaching, while leading the security champions network and authoring widely adopted secure-coding guidelines.
Technical Skills
- SDLC & Shift-Left:
- Threat modeling integration, secure design reviews, security gates in CI/CD, requirements-phase security analysis, release-gate sign-off
- Threat Modeling & Design:
- STRIDE, PASTA, attack trees, MITRE ATT&CK mapping, Microsoft Threat Modeling Tool, data-flow diagrams
- Code Review & Languages:
- Java, Python, JavaScript / TypeScript, Go, C#, Ruby, manual + tool-assisted review, business-logic flaws
- AppSec Tooling:
- Semgrep, SonarQube, Checkmarx, Veracode, Burp Suite Pro, OWASP ZAP, Snyk, Dependabot, Mend
- OWASP & Vuln Expertise:
- OWASP Top 10 (web + API), ASVS, SAMM, CWE / CVE analysis, injection, SSRF, IDOR, deserialization, XXE
- API & Microservices:
- REST, GraphQL, gRPC, OAuth 2.0, OIDC, JWT, RBAC / ABAC, rate limiting, schema validation
- Auth, Crypto & Secrets:
- TLS configuration, OAuth flows, MFA, password hashing (Argon2, bcrypt), HashiCorp Vault, KMS guidance
- Bug Bounty, Pentest & Metrics:
- HackerOne, Bugcrowd, pentest vendor management, vulnerability triage, MTTR scorecard, security champions program
Education
Work Experience
- Lead application security across the Dropbox engineering SDLC spanning 180+ repos and 240+ services, coordinating threat modeling, secure code review, and security tooling with influence across 350 engineers across 18 product teams.
- Run threat-modeling sessions using STRIDE and attack-tree analysis on every greenfield design, leading ~28 sessions per quarter and shipping documented mitigations on 94% of high-risk threats before code merge.
- Operate the secure code-review program across 180+ repos in Java, Python, and Go, cutting net-new vulnerability introductions from 42 to 9 per quarter through targeted pattern reviews and shift-left education.
- Tune Semgrep SAST and Snyk SCA across the monorepo, closing 3,400+ findings in the past year and holding false-positive rate under 8% through curated rule sets and policy-as-code triage.
- Drive OWASP ASVS Level 2 coverage across tier-1 services, mapping controls into Jira and clearing all 14 high-risk OWASP Top 10 categories before the SOC 2 audit window.
- Hardened 128 REST and GraphQL APIs with OAuth 2.0 + OIDC + JWT auth, RBAC + ABAC authorization, and schema validation per the OWASP API Security Top 10, retiring 22 broken-object-level-auth patterns.
- Manage the HackerOne bug bounty program handling ~140 valid reports per year, triaging and resolving findings within an MTTR (critical severity) of 6 days (down from 22 days).
- Built the security champions network of 24 engineers across all product teams, running monthly office hours and a 6-week secure-coding curriculum that 120+ engineers completed.
- Built the AppSec scorecard tracking MTTR on critical vulnerabilities, cutting from 34 days to 8 days over 24 months through tightened SLAs and exec-level monthly reporting.
- Mentored 5 mid-career engineers through OSCP, CSSLP, and AWS Security Specialty paths, and co-authored the team's secure-coding wiki adopted by 4 sister teams.
- Partnered with Platform, SRE, and Privacy teams across 6 product surfaces, authoring 18 secure-coding runbooks and onboarding 3 new AppSec engineers into the team's review workflow.