Twitter is apologizing for an embarrassing “human error” involving its latest app.

The Vine app, which could be a boon for PR professionals, enables Twitter users accessing the site with their iPhones or iPod Touches to display a six-second video in their tweets. Atop the Vine app is a video designated as the “Editor’s Pick”; this is the first thing visitors see when they open the app.

For a brief time on Monday morning, the “Editor’s Pick” was a “hardcore” pornographic video, according to The Verge. Although Twitter noted that the video contained “sensitive content,” it still reportedly riled a number of users of the app.

Later Monday morning, after the video had been taken down, Twitter apologized. A spokesperson for the company told Mashable:

“A human error resulted in a video with adult content becoming one of the videos in Editor's Picks, and upon realizing this mistake we removed the video immediately. We apologize to our users for the error.”

The human error cited in the apology underscores what several tech blogs have called Vine’s “porn problem.” Six-second pornographic clips have proliferated on Twitter thanks to the app, which could prompt App to remove it from the app store due to the sexual content, according to tech blog SlashGear.

As part of its response to the problem, a Twitter rep told Business Insider that Vine users can flag content as inappropriate.

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