jQuery and Legacy Front End Penetration Testing
The screens nobody wants to reopen are still serving customers, and they are still in scope for your auditor. We test them as they are, then tell you what to patch, what to isolate and what to retire. CREST-certified testers, fixed price from £2,890, scoped in 24 hours.
- Unlimited retesting
- No rescheduling or cancellation fees
- Fixed quote within 24 hours
“I would highly recommend EJN Labs to any organisation seeking reliable, detailed, and well-managed penetration testing services, particularly for government or enterprise-level projects.”
Imran SaghirProject Lead, SquareOne“There wasn’t another company we could find that could deliver what we needed in the timeframe we needed. The client loved it, and we got instant ROI from the engagement.”
Dan WilcocksonCo-Founder, CelloriOld front ends fail in ways modern frameworks removed by default. Markup written directly into the document, selectors built from the URL, inline handlers, and no content security policy to contain any of it. The code has not changed in years, so neither have the bugs.
Legacy screens are not a smaller risk. They are an unattended one.
The second problem is the join. Most estates now run an old area and a rewritten area on the same domain and the same session, so a flaw in the part nobody maintains reaches the part everybody does.
The third is decision support. It is not useful to be told that a nine-year-old library has forty advisories. It is useful to know which ones are reachable in your application, what the exploit looks like, and whether the answer is a patch, a proxy rule or a retirement date. That is what this report gives you.
ISO 27001, SOC 2, PCI DSS and Cyber Essentials Plus audits accept manual penetration test evidence. Scan-only evidence is generally insufficient.
LEGACY SPECIFICS
What We Actually Test in a Legacy Front End
Ten test areas that apply because the front end predates the current stack, on top of the standard application checks. Every finding is verified, reproducible and mapped to OWASP, CWE and CVSS 3.1.
jQuery DOM sinks
Markup written from URL data, selector injection, and the handful of calls that turn data into executable content.
Library versions
Known issues in the versions actually deployed, including prototype pollution and selector flaws, and whether they are reachable.
Unmaintained plugins
Sliders, date pickers, upload widgets and grid plugins that stopped receiving fixes years ago.
Inline handlers and evaluation
Event attributes built from data, evaluation of strings, and timers that execute code from variables.
Content security policy
Whether a policy is possible without a rewrite, and what a realistic first policy looks like for an inline-heavy page.
Old and new sharing a session
What a flaw in the legacy area reaches in the modern one, and whether the session boundary is really a boundary.
Forms and request forgery
Tokens missing on older endpoints, weak referer checks, and state-changing requests that accept a simple form post.
Client side trust
Hidden fields, disabled inputs, prices and roles supplied by the browser and accepted by the server.
Server rendered remnants
Classic ASP, old PHP includes and JSP fragments still reachable, including files nobody knew were published.
Upgrade path
Findings grouped into patch, isolate and retire, with the effort each one takes, so the remediation plan writes itself.
METHODOLOGY
What a legacy JavaScript finding looks like
Written the way a finding appears in our reports. The example below is reconstructed from publicly documented research, with hosts, paths and identifiers redacted. We do not republish client findings, named or anonymised.
jQuery HTML manipulation restores script that the server side sanitiser had removed
- Affected
- The internal messaging view at [redacted], jQuery 3.4.1 loaded from a bundled vendor file that had not been updated since the application was built.
- What we found
- Content was sanitised on the server, then passed to the jQuery html method in the browser. On the version in use, certain elements were re-parsed in a way that restored an event handler the sanitiser had stripped, and the payload executed.
- Why it matters
- Stored cross-site scripting reaching every user of the messaging view, defeating the server side sanitiser the team had treated as the control.
- Fix
- Upgrade jQuery to 3.5.0 or later, use the text method for untrusted content, and sanitise on output with a maintained library rather than relying on input filtering.
Reconstructed from public research: CVE-2020-11022 and CVE-2020-11023, cross-site scripting in the jQuery HTML manipulation methods.
Legacy Front End Penetration Testing: From Scope to Attestation
CREST-aligned methodology built on OWASP Web Security Testing Guide, OWASP ASVS, NIST SP 800-115, and PTES. Each finding maps to all four standards plus your specific compliance regime.
Reconnaissance
Application mapping, technology fingerprinting, content discovery, parameter enumeration, authentication-flow analysis, role-matrix construction.
Vulnerability Assessment
Authenticated and unauthenticated automated scanning across every user role, plus targeted manual checks for known weakness patterns.
Manual Exploitation
Hands-on testing by a CREST-certified pentester. Business-logic exploitation, chained vulnerabilities, privilege escalation, impact validation.
Reporting + Retest
Executive summary, technical report with CVSS scores and reproduction steps, walkthrough call, free retest after remediation, attestation letter.
CREDENTIALS
Verified Accreditations Auditors Accept
Every credential below is independently verifiable. UK procurement teams, FCA supervisors, ISO 27001 / SOC 2 auditors, and cyber insurance underwriters all recognise these standards.
GET YOUR QUOTE
Get a CREST Legacy Front End application pen test quote in 24 hours
A fixed-price quote back in one business day, from a named CREST assessor. No sales pipeline, no chasing.
- CREST and IASME accredited. Testing your auditors and clients already recognise.
- Fast-track testing within 24 hours where required. Free retest of every fix included.
- Live findings via your client portal, not a four-week PDF.
- Fixed price from £2,890 for a small, single-scope engagement, agreed up front. Most engagements run £4,560 and up. No day-rate surprises.
Dan WilcocksonCo-Founder, CelloriUnder NDA Further named references available on a scoping call.
- We reply within one business day with a fixed-price quote from a named CREST assessor.
- You approve the scope and we book a start date, usually within 24 hours.
- Live findings land in your client portal as we test, with a free retest of every fix.
Get your fixed pen test quote in 24 hours
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COMPLIANCE READY
Reports Mapped to Every Framework
Findings are explicitly tagged to the relevant control reference. Your audit team submits the report directly without translation work.
ISO 27001:2022
Annex A.8.8 management of technical vulnerabilities plus A.5.15-5.18 and A.8.2-8.5 access control validation.
SOC 2 Type I & II
CC6 logical access, CC7 system operations, CC8 change management evidence.
PCI DSS
Requirement 11.4 application penetration testing across cardholder data environments, including ecommerce penetration testing for online retail platforms.
FCA SYSC
SYSC 4.1.1R, 6.1.1R, 13 mapped to each finding for FCA-regulated firms.
UK GDPR
Article 32 effectiveness testing, customer-data security controls, ICO-acceptable evidence.
Cyber Essentials Plus
Direct certification through our IASME body status, single-vendor delivery.
PRICING
Transparent Legacy Front End Penetration Testing Pricing
Pricing depends on app complexity, user-role count, business-logic depth, and integration surface. The day count flexes; the included deliverables stay the same across all engagements.
2 to 4 days
Single user role, basic CRUD application, marketing website with auth. Typically 5-day engagement.
Get a fixed quote4 to 5 days
Multi-role SaaS, business application with payment integration. Typically 8-12 day engagement.
Get a fixed quote5 to 8 days
Multi-tenant platform, complex authorisation matrix, integration-heavy applications. 15-20 day engagement.
Get a fixed quotePart of Technologies We Pen Test. These are examples of the stacks we publish pages for, not a complete list. If yours is not here we still test it. Related pages:
BY SECTOR
Legacy Front End Penetration Testing for Your Sector
Sector-specialist scoping for UK businesses with sector-specific compliance regimes and threat models.
Fintech & FCA-Regulated
FCA SYSC, Open Banking FAPI 1.0, PSD2 SCA, payment-flow scrutiny, KYC/AML testing.
Fintech sector pageSaaS Companies
SOC 2 Type I & II evidence, multi-tenant boundaries, role escalation, customer-tenant isolation.
SaaS sector pageLaw Firms
SRA Cyber Standard, privileged data, conveyancing fraud defence, partner-tier procurement.
Law firm sector pageHealthcare
NHS DTAC, DSP Toolkit v6, UK GDPR Article 32, EHR systems, telehealth platforms.
Healthcare sector pageInsurance
FCA / PRA Operational Resilience, cyber underwriting, claims data, broker portals.
Insurance sector pagePublic Sector
CCS / G-Cloud framework, NCSC-aligned, citizen-facing services, PSN-compliance scrutiny.
Public sector pageWHY EJN LABS
What You Get From Legacy Front End Penetration Testing
Six concrete differentiators competitors don’t all match.
CREST-Certified Testers, Verifiable
Every test by a CREST-certified pen tester (CRT, CCT APP, CCT INF where applicable). Verify our company status at crest-approved.org.
24-Hour Startup, Where Required
From signed scope to active testing in a single business day for incident response, audit deadlines, or regulator-driven timelines.
Live Findings, Not 4-Week PDFs
Critical issues reported during testing through your client portal. Your team remediates while testing continues.
Audit-Ready Reports
Executive summary plus full technical report with CVSS scores and explicit framework mappings (ISO 27001, SOC 2, PCI DSS, FCA SYSC).
Free Retests, Standard
Verify remediation of every finding before close-out. Letter of attestation for audit submission included. Most competitors charge £1,500-£3,000 per retest.
UK-Based CREST Testers
Every engagement performed by vetted, UK-based CREST-certified testers, matched to your needs, security clearance, and compliance scope.
FAQ
Frequently Asked
Is it worth testing something we plan to replace?
Usually yes, because the replacement is always later than planned and the old screens stay reachable in the meantime.
Can you tell us what to fix first?
That is the last test area on this page. Findings come grouped into patch, isolate and retire with effort estimates.
Will you break the application?
We agree destructive limits before we start, and legacy code gets a lighter touch on anything that writes data.
Do you cover AngularJS 1.x?
Yes, and the Angular page covers it too. Either scope works, we will tell you which fits your estate.
What if the code is not maintained by us any more?
Common. We report against what is deployed, and the recommendations are written so a third party can act on them.
Does this satisfy an auditor?
Yes. The report is the same format as every other engagement and maps to ISO 27001, SOC 2 and PCI DSS.
What is included in the price?
Scoping, testing, the executive summary, the technical report, a walkthrough call and free retests until the finding is closed. One scope, one number, no follow-up invoices.
How fast can you start?
Scope to active testing in 24 hours once the scope is agreed, subject to tester availability in your window.
Are your testers CREST certified?
Yes. EJN Labs is a CREST member company and testing is delivered by CREST-qualified testers. The membership is verifiable on the CREST marketplace.
20+ CREST-accredited testing services in one place
Web, mobile, API, cloud, AI, infrastructure, red team. Pick the test that fits your environment.
Get the old screens tested too
Tell us what is still running and where. You will have a fixed scope and a number within 24 hours.
