www.wysiwygwebbuilder.com

I installed the extension ecwid in my WYSIWYG Web Builder/system/extensions folder. Norton antivirus popped up two different windows stating that ecwid - language.wbx and and ecwid - minicart.wbx were flagged and removed for Threat name: WS.Reputation.1 respectively. Can you tell me why these items contain this threat and what is done to verify the software being downloaded from this site is safe to use?

There is no threat at all! it is simply a 'false' positive from Norton!. It is because 'Norton' doesn't recognise it from its definition database and simply sees it as a threat and throws a wobbly and goes into defensive mode. It is safe to install.
Please add the extension(s) to the exception list of 'Norton'.

There is no virus in WYSIWYG Web Builder or any of the available extensions.
This is a false positive, an error in your anti virus software.