M&A and the API Timebomb

Hey there!

Mergers and acquisitions are a landmine of integration challenges—from aligning teams to merging infrastructure. But one of the biggest blind spots remains API security.

Every deal comes with its own legacy: undocumented endpoints, forgotten microservices, staging environments left wide open. And yet, most due diligence checklists barely scratch the surface of the actual attack surface.

That’s the API timebomb amd most teams don’t even know they’re sitting on it.

Shadow APIs Love Chaos- Obviously!

When two companies merge, API sprawl doubles overnight.
Some services are still in use. Others are deprecated but never decommissioned.
And guess what attackers love? Endpoints that no one’s watching.

APIs from acquired systems often:

• Lack proper authentication

• Still call outdated third-party services

• Expose sensitive data via debug or dev parameters

If no one has a full inventory post-acquisition, you’ve created the perfect blind spot.

Security Is Rarely in the Room

Ask any CISO who’s been through a merger. Legal and finance are there from Day 1. Product and engineering show up next. Security?

They’re often brought in after the deal is closed when it’s too late.

By then, attackers may have already started probing the newly expanded surface area.

Due Diligence does not mean Security Diligence

Most due diligence focuses on IP, revenue, and customer data.
But what about:

• What APIs exist?

• Which are exposed to the internet?

• Who owns them?

• How are they secured, if at all?

These questions are rarely asked until a breach happens.

I’ve seen companies post-acquisition where security teams had no visibility into the APIs they inherited.

Sometimes, these were legacy SOAP APIs still running under the radar.
Other times, modern REST endpoints with zero authentication were quietly exposing customer data.
In one case, staging environments from a three-year-old product were still live with admin access wide open.

API sprawl becomes unmanageable overnight

When two companies merge, you’re inheriting every API they’ve ever built.

✅ Old endpoints no one’s maintaining
✅ Dev environments still live in the wild
✅ APIs with hardcoded secrets or test data
✅ Unpatched legacy gateways
✅ Zombie APIs that predate current staff

And worst of all? No one has the full picture.

The acquiring company thinks the acquired team has documentation.
The acquired team thinks it’s all in the handover.
In reality, it’s all chaos.

M&A multiplies risk, but not visibility

Here’s what I’ve seen firsthand in post-acquisition security audits:

• APIs calling deprecated internal systems, still using default credentials

• Internal services exposed externally via misconfigured load balancers

• APIs transmitting PII over HTTP—yes, still in 2025

• Logging endpoints silently leaking sensitive request bodies to third-party tools

And let me be very clear:
These are companies with massive market share.
Because scale doesn’t equal security not when visibility is fragmented.

Take Control

If your team is navigating—or planning—an acquisition, API security has to be on the table from Day 1.

• Build an immediate post-acquisition API inventory.

• Review access controls across all environments.

• Audit for shadow and zombie APIs.

• Set up monitoring before attackers do.

The earlier you do this, the less likely you'll need to explain an avoidable breach.

Final thoughts

Every merger is a turning point.
You can either inherit risk—or neutralize it.
You can either let APIs sprawl—or secure them with intent.

But it starts with knowing what you’re walking into.

And if your team is in the middle of—or preparing for—an M&A, don’t wait until you’re scrambling after a breach.

This is what I help companies solve. Before it becomes a headline.

👉 Book a free consultation with me here.
👉 Follow me on LinkedIn to stay up-to-date with the latest in API security.

See you in the next one. 🔥

Talk soon,
Damilola