Auction site eBay is investigating after users in the United Kingdom were left wondering if the site was hacked after its U.K. email account featured an image of a naked woman.

Buyers and sellers aired their grievances on social media and shared how baffling it was to see an avatar featuring a scantily-clad woman wearing only underwear on the email profile of a major business, the Daily Mail reported.

Twitter user @chlo_imrie shared the photo of the topless woman, saying, “Umm @eBay wtf why is this your email picture.”

Umm @eBay wtf is this why is this your email picture pic.twitter.com/1MqbmJh8rv — chlo 🏴🇺 (@chlo_imrie) September 6, 2019

Another Twitter user, Gavin Storey, said he was a “little bit concerned” by the profile image the auctioneer used for its email address:

Little bit concerned by the profile image @eBay have decided to use on their email address. Certainly not something I've done, so might be worth looking at on their end, I reckon… pic.twitter.com/ZsP5d3VtVi — Gavin Storey (@GavvieUK) September 6, 2019

A Twitter user by the name of Jack also chimed in, questioning why the email profile picture would feature a pornographic image:

Why is the eBay email profile picture porn? pic.twitter.com/jgrlWLHcn2 — jack 🇲἟✨ (@jackedonija) September 5, 2019

The BBC reported that the image appeared at the top of eBay U.K.’s messages containing notifications, receipts, and status reports for Microsoft Outlook mobile app users.

Once Microsoft applied an update to fix the flaw in the app, eBay’s icon returned to its familiar logo, according to the BBC.

News about the icon’s appearance circulated on Twitter and on the CasualUK Reddit forum.

EBay told the U.K. tech news site The Register that it was “investigating the root cause” of the incident.

“We are in touch with Microsoft– one of our email service providers in the UK– who is actively investigating the root cause of the matter,” said an eBay spokesperson, according to The Register. “Microsoft has assured us that they’re taking all the necessary steps to address the issue.”

The U.S.-based online auction company also said there was no reason to think user data or systems had compromised the change in icon.

Microsoft also said it would be looking into the incident.