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Outlook bug self-downloads empty 'TokenFactoryIframe' file to Macs

A faulty server-side update released to Outlook causes "TokenFactoryIframe" to automatically download itself when Safari users visit the web version of Microsoft Outlook.

The file, which has a size of 0 KB is automatically downloaded to the Mac's hard drive. The file does not have a file extension and cannot be opened.

The download occurs when visiting Outlook via Safari on macOS. Sometimes, the file may attempt to redownload itself every few seconds. The problem does not appear to exist on Windows-based machines.

Some users initially believed the file could be malware. However, the file, while annoying, is harmless. The file's original purpose was to act as an element to serve interactive content or videos on the site.

An investigation by Windows Latest found that it's merely a server-side issue caused by a faulty update. The issue does not appear to be related to Safari or macOS.

Reports from Reddit suggested that the issue began on Monday, May 2.

A Microsoft spokesperson acknowledged the issue while stating that users can resolve it in the meantime by switching to other browsers to access the email service. However, some users reported the same problem on alternate browsers like Firefox.