MS16-088: Description of the security update for Excel 2016: July 12, 2016

This security update resolves vulnerabilities in Microsoft Office that could allow remote code execution if a user opens a specially crafted Office file. One change that's included in this update applies to how Excel handles documents that are opened from untrusted locations that are not supported in Protected View. These include untrusted Excel add-ins (.xla or .xlam) and HTML content (.htm or .html, including those documents that are renamed with an .xls extension). Previously, these files bypassed Protected View when opened. This could lead to a security vulnerability. This security update now blocks these files from being opened from untrusted locations. This security update may break compatibility with existing solutions. To work around these issues, users have to manually trust the file before they open it in Excel. 

For more information about Office trusted locations and how to trust a file, see the following Microsoft webpage: Alternatively, follow these steps to manually unblock an Excel add-in (.xla or .xlam).

Note This action cannot be undone.

1. Locate the .xla or .xlam file in File Explorer.
2. Right-click the file, and then click Properties.
3. Click the General tab, and then in the Security area, select the Unblock check box.
4. Click Apply, and then click OK.

After you do this, the Excel add-in will be available and appear as expected.



Important We do not recommend that you uninstall any security update. Doing so will leave your system vulnerable.

The Office security team is considering changes in future updates to preserve security and to help customers resolve any workflow issues that are caused by this security update. For more information, see the following Excel Support team blog:

Security update deployment information

For deployment information about this update, see Microsoft Knowledge Base article KB3170008.

Security update replacement information

This security update replaces previously released security update KB3114964.

File hash information