Web application security testing is not one activity, it is a set of methods that each catch different problems. Teams get into trouble when they assume one type covers them. This guide breaks down the main approaches, what each finds and misses, and how to combine them into real coverage.
The types of web application security testing
SAST (Static Application Security Testing). Analyzes source code without running it, catching insecure patterns early in development. Strong on breadth and coverage of the codebase. Blind spot: no view of runtime behavior, and it generates false positives that need triage.
DAST (Dynamic Application Security Testing). Tests the running application from the outside, like an automated attacker. Finds issues that only appear at runtime. Blind spot: no view of the code, misses business logic, and only tests the paths it can reach.
IAST (Interactive Application Security Testing). Instruments the running app to combine static and dynamic views, more accurate than either alone. Blind spot: requires instrumentation and still misses design and logic flaws.
SCA (Software Composition Analysis). Scans your third-party dependencies for known vulnerable components, essential given how much of any app is open-source code. Blind spot: says nothing about your own code.
Manual penetration testing. A skilled human attacking the application with intent and creativity. This is where the flaws that cause real breaches surface: business logic abuse, chained exploits, and authorization gaps no scanner conceives of. Blind spot: point-in-time, and its value scales with tester skill.
What automation cannot catch
The most damaging web vulnerabilities require understanding what the application is supposed to do, then abusing that intent. Scanners have no concept of intent, so they consistently miss:
- Broken access control and IDOR, whether one user can reach another’s data, the most common serious finding
- Business logic flaws, abusing legitimate workflows in unintended ways
- Chained exploits, combining several low-severity issues into one critical impact
This is why manual testing remains irreplaceable, and why we go deeper on it in automated vs manual penetration testing.
How to combine them
Layer the methods by where they fit in your lifecycle:
- In development: SAST and SCA run continuously in the pipeline, catching known issues before code merges.
- In QA / staging: DAST (and IAST if instrumented) tests running builds.
- Before major releases and on a regular cadence: manual penetration testing for the deep, adversarial coverage automation cannot provide.
We lay out the full layered model in a layered approach to AppSec testing.
The takeaway
No single method secures a web application. Automated tools give you breadth and speed; manual penetration testing gives you the depth that finds real breaches. The teams that stay secure run both, continuously for the routine, periodically for the sophisticated.
If you want the deep, human layer that anchors real web application security testing, scope a web application penetration test and we will find what the scanners have been missing.
Written by
Invadel Team
Senior penetration testers writing from real engagements — the same team that scopes, tests, and reports for our clients. About Invadel →