When FBI agents showed up at her house, they say she confessed to “removing the classified intelligence reporting from her office space, retaining it, and mailing it from Augusta, Georgia, to the News Outlet.” She faces up to 10 years in prison.

Given what is in the public record from the FBI complaint, Winner was almost certain to get caught, and some have argued that The Intercept could not have prevented that. Obviously, the NSA monitors and records who prints what documents. There’s an audit trail there, which one imagines an NSA contractor would know.

That’s why many in the computer security have deemed the way the leak was made and handled to be a terrible example of “operational security,” or as you’ll see it relentlessly abbreviated, “opsec.”

The Intercept released a statement today, however, reminding people not to take the FBI’s complaint as fact.

“While the FBI’s allegations against Winner have been made public through the release of an affidavit and search warrant, which were unsealed at the government’s request, it is important to keep in mind that these documents contain unproven assertions and speculation designed to serve the government’s agenda and as such warrant skepticism,” they wrote. “Winner faces allegations that have not been proven. The same is true of the FBI’s claims about how it came to arrest Winner.”

If Winner wasn’t found the way the complaint claims, the mysterious dot code is one other way the FBI could have found her, as the research blog Errata Security spelled out in detail.

In fact, the document that The Intercept published contains these dots, and the code spells out a date—May 9—that matches the FBI affidavit’s account of Winner’s printing. It also notes a serial number, which the NSA could obviously match back up to a machine in their offices.

Let’s invert the colors.

And then crank up the brightness of the dots.

As you can probably see now, the dots are printed in a repeating rectangular pattern. They’re a code. And the Electronic Frontier Foundation cracked it some years ago, at least for Xerox printers.

Let’s look at the rectangular code up close.

Errata Security says that the pattern was flipped upside down, so let’s flip it.

Then they used the EFF decoder, which I’ve combined with the original image here, so you can see the pattern more easily.

Run through EFF’s parser, Errata Security found that it output a time of 6:20, a date of May 9, and a couple of possible serial numbers. As Errata Security notes, “The NSA almost certainly has a record of who used the printer at that time.” If they didn’t already have Winner in some other way, this would probably have sealed her capture.

As one might expect, the EFF has some strong opinions about these dots, and their inclusion in the firmware that runs color laser printers. They’ve been tracking the use of these dots for a decade.