The reference website Wikipedia was targeted by a vandal on Monday who edited a template used to support page functionality to show a Nazi flag. A number of social media users were shocked to discover that swastikas appeared across the site after reporting the issue.

People would not be able to view pages that were created by actors or politicians. Instead, they would only see the Nazi symbol on a background and no text.

Wikipedia was back to normal after the problem occurred at 10 a.m. ET/7:00 PT.

Wikipedia’s Wikimedia Foundation described the incident as “particularly horrible” and stated that volunteers had identified the vandalism and reversed it within five minutes. The volunteers made modifications to the template within 15 minutes of the hate symbol being displayed on the site to protect it from vandalism.

A spokeswoman from Wikimedia stated that “In the spirit open editing and assuming goodness, this is not a step seldom taken with any Wikipedia areas unless an incident like this warrants it.”

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Wikimedia stated that the account responsible was blocked because it violated a number Wikipedia policies. It will continue to evaluate the situation and determine if additional action is necessary.

Due to its open-source nature, Wikipedia has been the subject of many inflammatory edits over the years, but in most cases they only affect a single article at a time. The Wikimedia spokesperson said that a variety of tools and processes had been created over the years to spot and reverse vandalism on the site. She also stated that Monday’s vandalism was quickly caught and reversed by administrators.