You can patch every server, train every member of staff, and lock down every login in your business, and still get breached through the accounting software vendor you have never met, sitting three steps removed from your own systems entirely. Supply chain risk is the uncomfortable reminder that your security perimeter now runs through companies you do not control at all. You chose them for their service, not for a security posture you were never shown in detail.
The Weakest Link Is Rarely Yours
Modern businesses run on integrations: a payroll provider with API access to your HR system, a marketing platform that syncs customer data automatically overnight, a logistics partner with a direct connection into your inventory database. Each integration is a legitimate business need and, simultaneously, a door into your systems that you did not build and cannot fully inspect from the outside, because it belongs to someone else’s infrastructure entirely, not yours. Most contracts describe what the vendor will deliver in great detail and say almost nothing about how the connection itself is secured.
Thorough API pen testing examines exactly these connection points, checking not just whether your own systems are secure but whether the access granted to third parties is scoped tightly enough that a compromise on their end cannot cascade straight into yours. Too often, a vendor integration is granted broad access during setup, purely for the sake of convenience, and never revisited again after that.
When Their Breach Becomes Your Headline
Regulators, customers, and journalists rarely care whose fault a breach technically was in the end. If your customer data leaked through a vendor’s compromised system, it is still your customer data, your regulatory obligation to report it, and your reputation absorbing the damage in the headlines the next morning, regardless of where the actual failure originally occurred. Explaining that the failure sat with a third party rarely softens the story much for anyone reading it.
William Fieldhouse sees this dynamic play out with almost every client engagement that touches third-party access in some form.
“We tested a client whose customer support platform, run by a third party, held full read access to their entire billing database for a feature that had not been used in over a year. Nobody had thought to revoke it once the project quietly wound down, and nobody was checking either, month after month.”
— William Fieldhouse, Director of Aardwolf Security Ltd
A full year of unnecessary access sitting quietly unused is exactly the kind of gap that never appears on an internal audit, because internally nothing about your own systems changed at all during that time. It takes someone deliberately mapping every third-party connection, not just your own infrastructure, to catch access that has simply outlived its original purpose and been forgotten. Nobody had done anything wrong; the access had simply never been asked to leave once the reason for it disappeared.
Audit the Doors You Did Not Build
Map every vendor integration your business relies on, confirm the access each one holds is scoped to what it genuinely needs today, and revoke anything left over from a feature or partnership that no longer exists. Pair that internal audit with proper external network pen testing to see your supply chain exposure the way an attacker actually would, looking in from the outside. It is a short exercise that rarely gets scheduled until something has already gone wrong.