Microsoft Outlook December updates trigger ICS security alerts

Trending 3 weeks ago


Microsoft is investigating an rumor that triggers Outlook information alerts erstwhile trying to unfastened .ICS almanac files aft installing December 2023 Patch Tuesday Office information updates.

Microsoft 365 users affected by this issue study seeing dialog boxes informing them that "Microsoft Office has identified a imaginable information concern" and that "This location whitethorn beryllium unsafe" erstwhile double-clicking ICS files saved locally.

"This behaviour is not expected erstwhile opening .ICS files. This is simply a bug and will beryllium addressed successful a early update," Microsoft explains successful this support document.

The institution besides revealed that nan information informing will beryllium displayed aft deploying a information update that patches nan CVE-2023-35636 Microsoft Outlook accusation disclosure vulnerability.

If near unpatched, nan information flaw tin beryllium exploited by attackers to instrumentality users of unpatched Outlook installations into opening maliciously crafted files to bargain NTLM hashes (their obfuscated Windows credentials).

The attackers tin later usage them to authenticate arsenic nan compromised user, summation entree to delicate data, aliases dispersed laterally connected their network.

​Workaround available

Until a solution is available, Redmond shared a impermanent hole for those impacted successful nan shape of a registry cardinal that would disable nan information notice.

However, erstwhile this workaround is deployed, it's besides important to statement that you'll extremity receiving information prompts for each different perchance vulnerable record types, not conscionable ICS calendars.

Those affected by this known rumor person to adhd a caller DWORD cardinal pinch a worth of '1' to:

  • HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\common\security (Group Policy registry path)
  • Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Security (OCT registry path)

Impacted customers tin besides disable nan dialog by pursuing nan step-by-step instructions disposable successful nan 'Enable aliases disable hyperlink informing messages successful Office programs' support document.

Microsoft fixed different known Outlook issue earlier this month, causing desktop and mobile email clients to neglect to link erstwhile utilizing accounts.

In December, nan institution addressed 2 much bugs causing problems for users pinch tons of folders when sending emails and 1 more causing Outlook Desktop clients to crash erstwhile sending emails from accounts.