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Web Application Penetration Testing Services

Web applications carry the majority of business risk for most modern organisations, customer-facing portals, internal admin systems, B2B platforms, API gateways, e-commerce checkouts. Each is a target for adversaries and a focus area for compliance auditors. Web application penetration testing is how you find the vulnerabilities before either does.

RedSecLabs delivers CREST-certified web application penetration testing covering the OWASP Top 10, OWASP API Security Top 10, business logic flaws, authentication and session weaknesses, and the language-specific issues that automated scanners systematically miss.

Every test combines tooling-driven breadth with manual depth on the application areas that matter most, authorisation, session management, business workflow, payment integration, file handling.

CREST Certified Pen Test Provider ISO Certified OSCP Certified Industry Certification

Free Security Quote

Just a few questions to scope your project. We respond the same business day.

✓ UK-based CREST member · ✓ QSA-aligned methodology · ✓ Same-day scoping response · ✓ Executive + technical reports · ✓ Retest included
Who this is for

This service is a fit if you’re..

1
Compliance evidence
SaaS preparing for SOC 2 Type II or ISO 27001 audits needing independent web app pentest evidence.
2
Pre-launch validation
Engineering teams launching a new product or major release wanting security assurance before customers do.
3
Customer security reviews
Vendors who keep failing the security questionnaire round of enterprise sales cycles.
OWASP
Top 10 + business logic
CREST
Certified testers
Manual
Senior tester depth
5-10 days
Typical engagement

What is web application penetration testing?

Web application penetration testing is the structured, predominantly manual assessment of web applications for exploitable security weaknesses. It covers the OWASP Top 10 (injection, broken access control, cryptographic failures, security misconfiguration, etc.) plus the much wider universe of issues those high-level categories abstract over, business logic flaws, race conditions, parameter tampering, mass assignment, IDOR variants.

Modern web application testing must also cover the API surfaces backing single-page applications and mobile clients, these often expose substantially more attack surface than the user-facing web pages themselves, with weaker authorisation enforcement and far more business-logic detail.

What web application testing delivers:

Identification of OWASP Top 10 vulnerabilities with exploitation evidence

Discovery of business logic and authorisation flaws

Validation of authentication and session management

API security testing for SPA and mobile backend interfaces

PCI DSS, ISO 27001, SOC 2 compliance evidence

Practical remediation guidance developers can act on

Most production web applications need at least annual testing, with additional testing after significant feature releases or architectural changes.

Why web application testing matters

Web applications are the most-attacked surface in modern enterprises. They expose business logic directly to the internet, often handle sensitive data, and present authentication boundaries that attackers actively probe. Vulnerabilities like broken access control and injection remain in the OWASP Top 10 year after year because they remain genuinely prevalent.

Compliance frameworks also focus heavily on web application security. PCI DSS Requirements 6.4 and 11.4 mandate application testing; ISO 27001 Annex A.14.2 covers secure development; SOC 2 CC8.1 expects evidence of change control including security testing.

Without quality web application testing, organisations risk:

Authorisation bypass enabling unauthorised data access

SQL and command injection leading to full backend compromise

Business logic flaws enabling financial fraud

Cross-site scripting (XSS) enabling account takeover

Authentication weaknesses enabling credential abuse

Compliance failures across PCI DSS, ISO 27001, SOC 2

Web application testing produces some of the highest-impact findings in any penetration testing programme, these are often the issues that directly enable headline breaches.

Who needs web application testing?

Any organisation operating internet-facing web applications or sensitive internal apps needs regular testing:

SaaS and B2B technology

Financial services and fintech

E-commerce platforms

HealthTech and clinical platforms

Payment and PSP systems

Government and defence

HR, payroll, and ATS platforms

AI and ML platforms

Any web application handling sensitive data or making authorisation decisions needs regular testing, at minimum annually, more frequently for high-risk or rapidly-evolving applications.

Our Web Application Testing Methodology

CREST-aligned methodology combining OWASP Testing Guide, OWASP ASVS, and bespoke manual review for business logic.

01

Scoping & Authentication Setup

We agree the in-scope application URLs, user roles, test account credentials, and any out-of-scope functionality. Authentication setup is critical, most weaknesses live behind login.

02

Application Reconnaissance

Manual application mapping, every endpoint, parameter, user role, business workflow, building a complete picture before exploitation.

03

Automated Scanning

Web scanners (Burp Pro, custom tooling) run against the application to surface pattern-matchable issues that become starting points for manual investigation.

04

OWASP Top 10 Testing

Systematic testing against each OWASP category: injection, broken access control, cryptographic failures, security misconfiguration, vulnerable components.

05

Business Logic Testing

The highest-value area, manual exploration of workflows, parameter tampering, race conditions, IDOR variants, mass assignment, function-level authorisation.

06

API & Backend Testing

Direct testing of API endpoints backing the application, often where the most exploitable issues live, with weaker authorisation than the UI implies.

07

Reporting & Walk-Through

Detailed findings with exploitation evidence, code-level remediation guidance, and live walk-through with your development team.

08

Remediation Retest

Critical and high findings re-tested after remediation, with documented validation for compliance evidence.

Typical engagement: 5-10 days for mid-complexity applications, 10-15 days for complex multi-role applications with significant business logic, longer for very large platforms.

What you receive

Every web application testing engagement with RedSecLabs includes:

  • Scoping document and signed rules of engagement
  • Executive summary for board and management consumption
  • Detailed technical findings with reproduction steps
  • CVSS plus exploitability prioritisation
  • Code-level remediation guidance with examples
  • Developer walk-through with engineering team
  • OWASP Top 10 and ASVS compliance mapping
  • Remediation retest of critical and high findings

Industries We Serve

We deliver this service across these industries:

Financial Services
Healthcare
SaaS & Technology
E-commerce & Retail
Defence & Government
Cloud & Managed Services
Education
Professional Services

Why RedSecLabs for web application testing

Web application testing rewards experience, the most damaging vulnerabilities are not scanner-detectable, they require senior testers thinking like attackers about business logic, authorisation models, and the gaps between what developers intended and what the application actually allows. We staff every engagement with senior application security practitioners, not generalists running Burp.

CREST-certified application testers
Manual business logic testing depth
Code-level remediation guidance
OWASP Top 10 and ASVS coverage
Developer walk-through included
Remediation retest in scope

Schedule Your Web App Pentest

Book a free 30-minute scoping call. Fixed-fee proposal within 48 hours, engagement starts within 1-2 weeks.

Book a Scoping Call Contact Us

Where to next

Related services and industry packages worth exploring.

API Pentesting

Mobile App Pentesting

Secure Code Review

Frequently Asked Questions

OWASP Top 10 coverage (injection, broken access control, cryptographic failures, security misconfiguration, etc.), business logic testing (workflow tampering, race conditions, IDOR, mass assignment), authentication and session management, authorisation testing across user roles, API backend testing, and client-side issues. Specific scope agreed during scoping.

Yes. SPAs and the APIs backing them are core scope. Modern web testing usually involves more API testing than traditional page testing, since SPAs push business logic into JavaScript with API backends that often have weaker authorisation than the UI implies.

We test all distinct authorisation roles in scope, typical mid-complexity applications have 3-5 roles (anonymous, user, admin, support, integration). Each adds testing time. We confirm the role matrix during scoping and price accordingly.

Web app pentesting is black-box or grey-box runtime testing, we test the running application. Code review is white-box static analysis of the source code. They find different categories of issues and are complementary. Many of our clients use both for high-risk applications.

Mid-complexity applications £6,000-£18,000; complex multi-role applications £15,000-£35,000; very large platforms £30,000-£80,000+. CREST premium adds 10-20%. Pricing reflects tester days, not licence costs. Fixed-fee quote within 48 hours.

We strongly prefer testing in pre-production environments equivalent to production. Where production testing is necessary, we use careful controls to avoid data corruption, read-only on critical data, isolated test accounts, no destructive testing without explicit approval. We discuss this thoroughly during scoping.
What you receive

Every engagement includes

  • ✓ Scoping call. A 30-minute call to define scope, timeline, and authorisation boundaries.
  • ✓ Test plan. Written test plan covering targets, methodology, and rules of engagement.
  • ✓ Technical report. Detailed findings with reproduction steps, evidence, and remediation guidance.
  • ✓ Executive summary. Board-ready 1-2 page summary with risk ratings and business impact.
  • ✓ Audit-ready evidence. Findings letter formatted for auditors, customers, and supervisory authorities.
  • ✓ Retest letter. Free retest of remediated findings within an agreed window. Confirmation letter included.
  • ✓ Remediation call. A call with our lead tester to walk through findings and remediation strategy.
How we deliver

Our process, end to end

  1. 1
    Scoping call & fixed-scope quote
    A 30-minute call. We define scope, targets, timeline. You get a fixed-scope quote within one working day. No surprise invoices.
  2. 2
    Test plan & authorisation
    Written test plan covering methodology, targets, and rules of engagement. Authorisation letter signed before any testing begins.
  3. 3
    CREST-aligned execution
    Senior tester runs the engagement. Critical findings flagged immediately during testing. Daily updates if you want them.
  4. 4
    Technical + executive report
    Detailed technical findings with reproduction steps. Board-ready executive summary. Delivered within agreed working days.
  5. 5
    Remediation call & retest
    Walkthrough with our lead tester. Retest of remediated findings within the agreed window. Confirmation letter for your auditors.
Engagement scope

What shapes the quote

Small scope
Single app, focused scope, smaller surface. 5-7 working days.
Medium scope
Multi-role platform, several user types, integrations. 8-12 working days.
Enterprise scope
Complex environment, multiple targets, compliance evidence. 12-25 working days.
Fixed-scope quote within 1 working day
No surprise invoices, no scope-creep. We commit to a number before you commit to us.
Sample report
See exactly what we deliver
Download a redacted RedSecLabs penetration test report. Same format, same depth, same clarity as the report your team will receive.
Download sample report
Why RedSecLabs

Grounded reasons clients choose us

⚑
UK-based team
Testers based in the UK. Data stays within UK/EU jurisdiction for sensitive engagements.
❄
CREST member company
CREST-aligned methodology. Senior testers hold CREST CRT or CCT certifications.
⚙
Manual testing, not scanner-only
Automated scanners catch the obvious. Our human testers find the issues that matter.
✎
Clear executive reporting
Reports your board can read and your developers can act on. No jargon padding.
♚
Compliance-aware delivery
PCI, SOC 2, ISO 27001, DORA, GDPR. We map findings to your compliance framework.
↺
Retest support included
Free retest of remediated findings within agreed window. Confirmation letter for auditors.
Related services

Often paired with this engagement

API Penetration Testing →
Test the APIs underneath your web app.
Mobile App Pentesting →
Companion iOS/Android testing.
AWS Cloud Pentesting →
Test the cloud infrastructure underneath.
Secure Code Review →
Pair with code review for layered assurance.
SOC 2 Compliance →
When pentest is part of a SOC 2 programme.
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