Why Did YouTube Mass Recommend That People Watch News Footage of the 9/11 Attacks?

If you’re not careful on YouTube, you can be endlessly served a conveyor belt of content curated specifically for you based off of your viewing habits. You like cooking vids? Game playthroughs? Late night show segments? There’s literally millions of those, one after another reliably waiting for you to get lost in.

But YouTube’s recommendation algorithm is broken. For example, researchers believe it plays a role in radicalizing people, by showing them more extreme content over time. And then there’s the just plain weird anomalies that sometimes happen with the algorithm.

Earlier this month, a two-hour newscast from CNN on the morning of the 9/11 World Trade Center attacks started showing up in the recommended section of many users’ feeds, prompting people to question, “What did I watch for this to be recommended to me?” The video itself was uploaded more than five years ago by an account exclusively full of other videos from Sept. 11, 2001 and news coverage of the attacks from that day.

Thousands of users have poured into the video’s comments section in the past week, many questioning why the video had been recommended:

Last week, people on Reddit began complaining about “weird shit” in their YouTube’s recommendations section (though not this video in particular.) It caught the attention of a YouTube community manager, who responded, “Just confirming that YouTube is aware of this thread and looking into it—we do think something weird is up.” The manager later confirmed that the issue was “fixed.” According to reporting from The Verge, YouTube declined to provide more information about what caused the issue.

A Google spokesperson also declined to provide more information to Motherboard, but said in an email that the 9/11 video was not related to the glitch from last week.

We don’t know for sure why this video keeps getting recommended, but its newfound popularity is probably feeding on itself. The thousands of comments from just the last few days and views on the video—which is now at 1.5 million, far more than most of the other videos on the channel—probably played a big role in it being recommended to more users. The mystery remains.