Microsoft: Outlook bug downloads ‘TokenFactoryIframe’ file on every visit

Outlook TokenFactoryIFrame

Microsoft’s Outlook is downloading a mysterious file called
TokenFactoryIframe” on macOS when users visit
the email service via the Safari browser. This issue has now
been widely reported by users who have discovered the
‘TokenFactoryIframe’ file that Outlook downloaded on every

Outlook downloads this mysterious file every few seconds or at
least on every visit to Outlook on Apple’s platform. According
to our findings, this appears to be an issue caused by a faulty
server-side update released to the Outlook and it has nothing
to do with Safari or macOS.

Microsoft acknowledged the problem in a statement, but the
company hasn’t revealed what’s causing the downloads. It’s
likely due to an error in the HTML of the Microsoft 365
platform as iframe is a well-known element used on websites for
hosting interactive content or videos.

Based on reports
from Reddit, it looks like the problem was first highlighted on
May 2 and it has been widely reported over the past two days.

Microsoft spokesperson said the problem is limited to Safari
and users can switch to any other browser to prevent this from
happening. However, we have received reports claiming the issue
can also affect Chrome and Firefox on Apple’s platforms.

What is TokenFactoryIFrame?

Following a recent server-side update to, users
noticed that a file called “TokenFactoryIFrame” started
appearing in Safari’s downloads section. The email client
reportedly downloads the file every few seconds and the
zero-byte file makes the site unusable.

Called an inline frame (iframe), it is an element used for
websites. It basically attempts to load another HTML page
within the document. This method is commonly used for web
advertisements, embedded videos, interactive content, online
games, and many other features.

TokenFactoryIFrame Outlook fix

Thankfully, the file is zero kilobytes in size and it’s
harmless, so you can manually delete it from the system without
worrying about consequences. However, there’s a catch –
removing it from the device’s storage is ineffective as the
file downloads again when you visit in Safari,
which is the default browser.

A Microsoft spokesperson confirmed that the company is aware of
an issue where Outlook forcefully downloads token factory
iframe on every visit to Outlook in a Safari browser on

“There is an ongoing issue affecting Outlook on the Web via the
Safari browser in which users are continuously prompted to
download a file titled “TokenFactoryIframe.” At this time, the
recommended course of action is to use an alternate browser,”
Microsoft officials said.

How to prevent Outlook from downloading TokenFactoryIframe

To fix TokenFactoryIframe issue in Outlook,
follow these steps:

  1. Launch Safari, but don’t log in to
  2. Head to the Preferences tab from the
    Safari menu at the top.
  3. Select Websites.
  4. Select Downloads in the left
    General column.
  5. This will present a list of websites with download
    permissions. As long as the download permission for Outlook and
    Office is disabled, the browser will stop downloading any file
    offered by Outlook.
  6. In the list of websites with download permissions, locate
    and deny all Outlook and
    Office entries.
  7. Once done, exit Preferences.

While this fixes the token factory iframe bug in Outlook, it
will also prevent the browser from downloading all attachments.

Thankfully though, you can switch to Chrome to avoid Outlook
problems, but this workaround may not work for everyone.

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