For a short time, YouTube's most popular video, a music video called "Despacito" by the artist Luis Fonsi with more than 5 billion views, was altered to feature imagery of a masked, gun-wielding gang from the Netflix show Casa de Papel. The video has since been restored to its original state.
The videos all appear to be official VEVO music videos, a video hosting platform partnered with YouTube and music labels, which could point to a hack that was specifically aimed at compromising VEVO.
In a statement to Business Insider, VEVO confirmed that a number of its videos were subject to a security breach, but said that the breach had since been contained.
"We are working to reinstate all videos affected in our catalogue to be restored to full working order. We are continuing to investigate the source of the breach," the statement read.
At the moment, details are still unclear and neither YouTube or Vevo have confirmed what was behind the hack, although multiple people are pointing to two Twitter users with the handles @Kuroi'SH and @Prosox, who have both claimed responsibility.
A Twitter user who goes by the handle @sh_kuroi and describes themself as a "security researcher" from Western Sahara "acting to support the freedom of my country" tweeted out that they had accessed YouTube CEO's Susan Wojcicki's account as well as that of Shakira's.
The account has also said its new targets are YouTubers Jake and Logan Paul.
A Twitter user called Prosox, who also identifies as hacker, claimed to have taken part in the hack as well, tweeting out, "Its [sic] just for fun."
It's important to keep in mind that neither of those two accounts claiming responsibility have been proven in any way to be behind the alterations of the music videos, and neither YouTube nor VEVO have said anything about any parties responsible.
YouTube is aware of the issue, and said in a statement to Business Insider that VEVO is investigating the issue.
"After seeing unusual upload activity on a handful of VEVO channels, we worked quickly with our partner to disable access while they investigate the issue," a YouTube spokesperson told Business Insider.