Please locate the security policy files which can be find in CuteSoft_Client\CuteEditor\Configuration\Security folder.
In the secuity policy file, you can find the following entry:
<security name="filenamePattern">^[a-zA-Z0-9\._-]+$</security>
Just modify this pattern to meet your own requirements.
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Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx