Dear Friends,

Due to various reason, software are saving HTML file as XLS and allowing users to open the file using excel software.

Users are getting the above error message, to avoid this error message, you can add the below entry in registry, so that this warning message will disappear while opening the file.

Excel 2007
[HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security]
“ExtensionHardening”=dword:00000000

Excel 2010
[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Excel\Security]
“ExtensionHardening”=dword:00000000

Excel 2013
[HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Excel\Security]
“ExtensionHardening”=dword:00000000

Thanks to IBM Support Team