If the dtsExoLimitExtensions flag is set, image and attachment filename extensions will be limited to the values listed in allowedExtensions.

The allowedExtensions option provides a way to guard against execution of malware that may be embedded in documents. When an attachment or image is extracted, unless the filename extension is one of the listed extensions in allowedExtension, the filename will have the defaultExtension appended to it. 

For example, if "exe" is not included in the list of allowedExtensions, and if the defaultExtension is ".data", then an attachment named "sample.exe" will be saved as "sample.exe.data". 

Separate extensions with spaces. Do not include the "." in each extension.