New Yorkers who opened up Snapchat, The Weather Channel, CitiBike, or a number of other apps and services this morning found that the name of their city had been swapped with anti-Semitic vandalism, replacing it with “Jewtropolis.”

The offensive change appears to have been a result of edits to Mapbox, a widely used service that powers the maps inside of all these apps and more. The change was also spotted inside the app for StreetEasy and on The New York Times’ map of 2016 election results. Mapbox also lists Vice, Vox (our sibling site), and the FCC as groups that have made use of its maps, however, the vandalism didn’t show up on those sites.

Snap tweeted that “Snap Map relies on third party mapping data which has unfortunately been subject to vandalism. We are working with our partner Mapbox to get this fixed immediately.”

Mapbox later responded with a statement calling the change “disgusting” and a “hate-speech attack.” The company said it has systems in place to make sure changes are valid, and that this one was initially blocked by AI. However, a human reviewer then approved the change, in what Mapbox is calling an error. “We will continue to investigate this act and make appropriate changes to further limit the potential for future human error.”

The changes appeared to be visible as early as 5AM ET, judging by a tweet sent at the time. By around 9AM, it appeared that the maps were in the process of being fixed, with the offensive name only being visible at certain view levels on some maps. Mapbox said it was able to remove the vandalism “within an hour,” however that seems to be more like an hour from when the change was starting to be widely noticed.

Online maps have been subject to vandalism many times in the past, often because individual users can suggest changes. A few years ago, someone edited Google Maps to place an image of Google’s Android logo peeing on an Apple logo somewhere in Pakistan. Google shut down the editing tool that allowed that to happen the next year. And just this week, Google Maps was edited to rename the Russell Senate Office Building after Sen. John McCain — something that has been proposed but has not yet happened. It was quickly reversed.

Those changes are less problematic, but they speak to the immense problems that mapping services open themselves up to by failing to vet changes that can appear in front of millions of people.

That seems to be what happened to Mapbox here. Though the company’s statement isn’t entirely clear on it, Mapbox says it sources mapping information from more than 130 data sets and that this change came from “a source” that has repeatedly attempted malicious edits — presumably a single user. Mapbox says it has a “strong double validation monitoring system” in place that catches 70,000 changes per day for human review. But that still requires humans to get it right; and as the last several years of online moderation have shown us, that doesn’t always happen.

Update August 30th, 12:19AM ET: This story has been updated with a statement from Mapbox.