Best Penetration Testing for SaaS
The best penetration testing for UK SaaS companies in 2026 comes from CREST-accredited providers who test multi-tenant isolation explicitly, cover both web application and API surface, include a retest for remediation evidence, and produce reporting that satisfies customer security questionnaires and SOC 2 or ISO 27001 evidence needs. This guide compares 7 providers: Precursor Security, NCC Group, Pen Test Partners, Redscan (Kroll), JUMPSEC, OnSecurity, and Bulletproof.
Seven penetration testing companies compared for UK SaaS buyers, on the criteria that actually matter for a multi-tenant product: isolation testing between customer accounts, API coverage, verifiable CREST accreditation, and reporting that survives an enterprise customer's security questionnaire.
We are Precursor Security, and we have ranked ourselves first on this list.
Rather than pretend otherwise, we publish the selection criteria in full and describe every provider fairly, including where a rival is the better fit. The firms below are genuinely good at what they do; the differences are in multi-tenant depth, transparency, accreditation, and who each serves best for a SaaS product. Confirm any CREST claim in the independent CREST member directory.
Seven firms, side by side
| Provider | CREST status | Pricing published | From |
|---|---|---|---|
| 1. Precursor Security | Pen Test + VA + SOC | Yes | From £2,500 |
| 2. NCC Group | Member firm | No | On application |
| 3. Pen Test Partners | Member firm | No | On application |
| 4. Redscan (Kroll) | Member firm | No | On application |
| 5. JUMPSEC | Member firm + NCSC CHECK | No | On application |
| 6. OnSecurity | Member firm | No | Instant quote via platform |
| 7. Bulletproof | Member firm | No | On application |
Verified against each provider's public website, August 2026. "No" under pricing means a rate was not published at the time of writing, not that a provider is more expensive. Redscan is part of Kroll (US-headquartered).
The 7 best for UK
SaaS in 2026
1. Precursor Security
Precursor holds triple CREST accreditation across Penetration Testing, Vulnerability Assessment, and Security Operations Centre. Testing covers web application and API surface together, which is where most SaaS risk actually sits, and includes multi-tenant isolation checks so a finding of one tenant reaching another's data gets caught before a customer does. Pricing starts from £2,500 at approximately £1,200 per consultant day, published on the website, with a retest included in every engagement and a written quote within 24 hours. Reports are built to stand up in the security questionnaires enterprise customers send during procurement, and findings feed detection rules through the closed-loop model, which suits a product that ships continuously rather than testing it once a year.
Trade-off: A UK mid-market specialist rather than a global enterprise brand, and it does not act as a SOC 2 or ISO 27001 certification body itself.
2. NCC Group
NCC Group is one of the largest security consultancies in the world, headquartered in Manchester, with a deep research pedigree and the capacity to staff very large assessment programmes across multiple products and regions. For a well-funded SaaS platform running a global security programme, few firms match its bench depth.
Trade-off: Engagement model and pricing are built for enterprise procurement. Costs are on application.
3. Pen Test Partners
Pen Test Partners are the UK's best-known specialists in embedded and operational technology, and their public research is consistently cited. For a SaaS company whose product touches connected devices or unusual infrastructure rather than a standard web and API stack, they belong on the shortlist.
Trade-off: A specialist focus; standard web application and API testing is not their distinctive strength. Pricing on application.
4. Redscan (Kroll)
Redscan, now part of Kroll, pairs a large practitioner organisation with the backing of a global incident response and forensics business. For a SaaS company that wants its tester, its IR retainer, and its forensics provider under one roof at enterprise scale, the Kroll relationship is the draw.
Trade-off: Kroll is US-headquartered, and the engagement model leans enterprise. Pricing on application.
5. JUMPSEC
JUMPSEC holds NCSC CHECK status alongside CREST membership, with a strong red teaming and adversary-simulation practice. For a SaaS vendor whose customer base includes public-sector or PSN-connected buyers who mandate CHECK delivery, that combination is the differentiator.
Trade-off: Pricing on application.
6. OnSecurity
OnSecurity runs a platform-first, pentest-as-a-service model with instant online quoting and quick scheduling. For an early-stage SaaS company that needs a test booked this week to unblock an enterprise deal or a funding round, the platform model works well.
Trade-off: Quotes are generated through the platform rather than published as a rate card, and the model suits smaller, repeatable scopes.
7. Bulletproof
Bulletproof combines penetration testing with a broad compliance practice, including Cyber Essentials and PCI DSS support, which suits a smaller SaaS company working toward its first compliance certifications and wanting one supplier to handle both.
Trade-off: A generalist breadth play rather than a testing specialist. Pricing on application.
How we ranked them for SaaS
Six criteria that matter specifically to a multi-tenant SaaS product, each something you can verify without taking anyone's word for it. Weighting is ours; the facts are checkable.
Whether the provider explicitly tests for one tenant reaching another tenant's data or functionality. It is the risk specific to SaaS, and a generalist who treats your product like a single-tenant web app will not scope for it unless you insist.
Whether the report format satisfies the customer security questionnaires enterprise buyers send during procurement, and provides the kind of evidence SOC 2 and ISO 27001 both expect around regular penetration testing.
Company and individual CREST accreditation, checkable in the public directory. It is the accreditation most enterprise customers and their security teams look for on a penetration testing supplier.
Whether verification of your fixes is included or sold back as a second engagement. Showing enterprise customers that findings were fixed and verified, not just found, is often what closes the security review.
Whether the scope covers both the web application and the API layer together, since most SaaS attack surface sits in the API a product exposes to its own frontend, integrations, and partners.
Whether findings feed ongoing detection rather than sitting in a PDF until next year. A product that ships continuously benefits from the closed-loop model more than a once-a-year test cycle.
Red flags for a
SaaS buyer
Whichever firm you choose, including us, walk away if you see these.
No multi-tenant or isolation testing
Ask directly whether tenant isolation is in scope. A generalist who treats your SaaS like a single web application will miss the exact failure mode, one customer reaching another's data, that matters most to your buyers.
A scan dressed up as a penetration test
Engagements priced under £500 a day are automated scans with a human cover sheet. Ask how many days of manual testing, by whom, with what certifications, and whether tenant boundaries were tested by hand.
POA-only pricing that stalls an enterprise sales cycle
A firm that cannot indicate a day rate before a discovery call adds procurement drag when an enterprise deal is waiting on your security review. UK CREST day rates run £1,000 to £1,500.
No retest, so no verified-fix evidence
A test without verification of your fixes is half a service. Enterprise customers increasingly want to see that findings were remediated and confirmed, not just listed in a report.
A generalist with no SaaS or API depth
Ask for a sample report or a summary of past SaaS-specific engagements. If the provider cannot describe API testing methodology or multi-tenant scoping specifically, standard infrastructure testing is probably what you will get.
Reports procurement teams will not accept
Ask for a redacted sample. If it reads like raw scanner output with no executive summary or clear remediation status, it will get rejected by the enterprise security team reviewing your vendor questionnaire.
SaaS penetration testing prices
CREST-accredited testing runs £1,000 to £1,500 per consultant day. At Precursor's published rate of approximately £1,200 per day: web application from £3,750, API security testing from £2,500, internal network from £6,250, and combined multi-scope SaaS assessments from £10,000. A worked breakdown with examples is on the cost guide.
Full cost guide with worked examplesMore on securing a SaaS product and the services referenced above.
Compare us against anyone on this list.
Multi-tenant isolation testing as standard. Fixed pricing published before you call. A written quote within 24 hours of scoping. Retest included.
Penetration testing for SaaS
The questions SaaS buyers ask most when comparing UK providers.
UK penetration testing runs from £2,500 for a small web application test to £25,000+ for a full multi-scope assessment, at roughly £1,000 to £1,500 per consultant day from a CREST-accredited provider. For a SaaS company specifically, budget for web application testing as a baseline, with API security testing added where the product exposes an API to customers or partners. Most SaaS platforms run this annually, or more often if the release cycle is fast. Most firms price on application; Precursor publishes its rates. A worked breakdown is on our penetration testing cost page.
Both SOC 2 and ISO 27001 expect regular penetration testing as evidence that technical controls actually work, not just that a policy exists. An independent, CREST-accredited penetration test, along with a report or summary you can share, supports both frameworks, and enterprise customers are increasingly asking for it directly in security questionnaires during procurement. Precursor delivers the penetration testing that feeds this evidence; it is not itself a SOC 2 auditor or ISO 27001 certification body, so your auditor or certification body remains a separate relationship.
Multi-tenant penetration testing checks whether one customer's account, on a shared SaaS platform, can reach another customer's data or functionality. It is the risk that is specific to SaaS and does not show up in a generic web application test: broken object-level authorisation, tenant ID manipulation in API calls, shared infrastructure misconfiguration, and privilege boundaries between organisations on the same platform. A generalist provider who treats a SaaS product like a single-tenant web app can miss this entirely, which is why it belongs as an explicit line item in the scope, not an assumption.
Most providers issue a full technical report at the end of testing, and many will also provide a shareable executive summary or letter suitable for a customer security questionnaire, but the format varies by provider. Ask each firm on your shortlist exactly what they issue, whether a redacted or summary version is available for prospects and auditors, and whether that is included in the price or billed separately. Get this in writing before the engagement starts, since it usually cannot be produced retroactively in a different format.
UK SaaS companies commonly shortlist a mix of specialists and larger consultancies. This guide compares seven: Precursor Security, NCC Group, Pen Test Partners, Redscan (Kroll), JUMPSEC, OnSecurity, and Bulletproof. The right choice depends on whether multi-tenant isolation is tested explicitly, whether pricing is published, whether a retest is included for your remediation evidence, and whether the report format satisfies enterprise customer security questionnaires. Confirm any CREST accreditation in the public directory at crest-approved.org.