BOPLA: The API Vulnerability That Lowkey Exposes Everything 😬

So, you know how APIs are kinda like the waiters of the software world?
You ask for something → they take your order → bring back the exact data you’re allowed to see.
Well… sometimes the waiter is bad at their job. And they bring your order plus your neighbor's confidential details, credit card limit, and last vacation location.

That’s what we call Broken Object Property Level Authorization (BOPLA) — previously known as:

• Excessive Data Exposure (API gives too much info)
• Mass Assignment (API lets users change stuff they shouldn't)

It’s basically when APIs don’t check which object properties a user should be allowed to read or modify.
And that’s where things can go real sideways.

Is the API Vulnerable? 🚨

If your API does any of the following, it's waving a giant red flag:

1. Exposes Sensitive Fields

Sending back full objects instead of only what’s needed.
Like, bro, don't expose recentLocation or fullName of someone being reported. Why is that even in the response??

2. Allows Users to Modify Object Properties They Shouldn't

Like allowing the client to decide how much something costs.
This is how someone ends up charging $1,000,000 for a room that costs ₹799 on a weekday 💀

Real-Life Attack Scenarios (And Why This Is Scary)

Scenario #1 — Dating App Snitching Gone Wrong

User reports someone → API responds with:

fullName
recentLocation

Buddy just wanted to report behavior, not stalk their house.
This is straight-up privacy leakage.

Scenario #2 — Marketplace Host Turns Into Jeff Bezos

Legit request:

{
"approved": true,
"comment": "Check-in after 3pm"
}

Host replays it but adds:

"total_stay_price": "$1,000,000"

Because the API never verified who can modify that field.

Now the guest gets financially traumatized.
Nice.

Scenario #3 — “Blocked Video? Nah, I’ll Just Unblock Myself 😎”

User tries updating video description:

{
"description": "funny cat video"
}

Replays with:

"blocked": false

API never checked if the user is even allowed to change the blocked state.
Result: the user unblocks their own censored content.

• BOPLA = API exposes or allows changes to sensitive object properties.
• Happens when field-level access control is missing.
• Leads to privacy leaks, privilege abuse, and fraud.
• Fix it by restricting what data is returned and what fields can be updated.