Worst Defect Ever: Experts Tell the Tale

Has a software defect ever kept you up at night? Was the defect so bad that it caused you physical pain, or even prompted a career shift? It happens.

In our discussions with software testing professionals and technology thought leaders, we often ask some hard-hitting questions about their past experiences with an application or product. These experts have seen some significant software defects over the years, running the gamut from amusing to frustrating to downright frightening. But which one was the worst?

We asked these experts the following simple, yet revealing question: “What is the worst defect you’ve ever encountered?” Let’s learn about these significant software defects — with names changed to protect the innocent.

Jane Doe

The worst defect I found actually sat in the defect log for four years before it got fixed. It was for a medical application, where doctors can enter medicines on neonatal patients. The standard configuration was for adult patients.

If you changed the configuration to go to neonatal patients and then you entered an allergy on that patient, it would not stop you from then entering the medication the patient was allergic to. So, it would let the doctor go ahead and place an order for penicillin on a neonatal patient that was allergic to penicillin, which is deadly. To me, that was a bad one. I just kept bringing it up every time we changed product managers until someone actually fixed it.

Sue Somebody

When I think about it from a usability point of view, the worst situation is when a user was convinced that they were successfully able to complete a task, but they actually weren’t. And so it’s one thing to have a user use a product and they can’t complete a task; they want to do X and they just cannot get it done for whatever reason. That’s bad. But [when an error message occurs] at least the user understands that there was a problem and they couldn’t complete the task. And, so maybe they’re unhappy, but they will go to another channel and they will use a website instead of a mobile app, whatever. But if the user actually thought that they successfully completed the task, but they didn’t, that’s really bad.

John Smith

My last company specialized and focused a lot of our attention on safety, critical systems. So, we found some really, really eye-opening bugs and systems. I’d say the worst, though, was we did find a defect in a nuclear reactor software control system that, in the right scenario, likely would have caused a nuclear meltdown of the nuclear reactor. But we found others that looked almost that bad too — there’s some scary stuff out there when it comes to defects.

Tom Foolery

One of them that still gives me nightmares is, when I was working for a bank, we pushed the wrong database into production, and it cost millions in losses. There was a lack of testing. Even in production, you have to do some kind of sanity checks before you roll it out to customers.

Penny Pincher

The worst one I ever encountered — and this was very early on in the development cycle, so it’s not like it went anywhere remotely near customers, thank goodness — was a login page where there was a username and password. If you logged in with the correct username and the incorrect password, you would be denied entry, or if you logged in with the correct password and incorrect username, you would be denied entry. But, if both your username and your password were wrong, you could get in. So that one was pretty bad.

And I’d also like to mention the funniest bug that I ever encountered. This is in a mobile application. There was a screen that had some data — I don’t remember what the data was, but you could refresh the data by hitting the refresh button. So every time you hit the refresh button, the screen would refresh and the new data would appear. But every time you hit the button, it got bigger. So it started out as a small button, and every time you hit the button in the screen, the button would get bigger and bigger and bigger and bigger until it went all the way across the screen. And I thought that was really amusing.

Walter Anyone

There’s been some doozies in my time, for sure. My all-time favorite bug was a car defect. So, the driver’s side had four controls for electric windows. You put the driver’s side window down and the [opposite side] indicator would come on. That’s a pretty good one.

[Another one was] there was a car that had two horns, one on each side of the steering wheel, so you could press one or press the other, and both would execute a horn. If you press them both at the same time, it would blow the fuse. The fuse that was used for the horn was also the fuse that was used for the radiator fan. So, if you hit both horns in rage, and you end up overheating your car and potentially blowing a head gasket. So that was a pretty cool one.

Joe Schmo

We did some testing for a company and found out their processor turned off all access to debit cards in Brazil. Brazil is a primarily cash-focused country; credit cards are slim. There’s a lot of cash-to-store and online options to pay, so not enabling debit cards for what was actually a couple-week period, they lost out on a ton of revenue for a simple mistake. The reputation, customer trust, customer feedback loop with you, that bridge sometimes can’t be unburnt. So, it’s definitely critical to take care of those things.

A. Nonymous

It was when I got to watch a customer use our code for the first time, and it was like the worst three hours of my life. I was with our chief architect and the lead developer. A certain routine operation that we expected people to do every week took 62 clicks. It was like being punched in the face for three hours in a row. That changed my career, because that’s when I got interested in UX and UI and feeding that into every stage of the delivery process.

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