Information
This policy setting determines whether Office applications can output graphics in Portable Network Graphics (PNG) format when documents are saved as Web pages. The recommended state for this setting is: Disabled. Excel, PowerPoint, and Word can save graphic files in Portable Network Graphics (PNG) format to improve the quality of the graphics when documents are saved as Web pages. The PNG graphic file format (.png) is used for a wide range of graphics, from small images (such as bullets and banners) to complex images (such as photographs), and can offer better image fidelity and smaller file sizes than some other formats. However, PNG graphics cannot be displayed by many earlier Web browsers, such as Microsoft Internet Explorer#x00AE; version 5 or earlier. By default, Office applications do not save graphics in the PNG format. To change this functionality, users can open the application's Options dialog box, click Advanced, click Web Options, and then select the Allow PNG as a graphics format check box. This setting can be used to guard against theoretical future zero-day attacks that might target PNG files.
Solution
To implement the recommended configuration state, set the following Group Policy setting to Disabled. User Configuration\Administrative Templates\Microsoft Office 2013\Tools | Options | General | Web Options...\Browsers\Allow PING As an Output Format Impact: Disabling this setting enforces the default configuration, and is therefore unlikely to cause significant usability issues for most users.