If you use software restriction policies as an application whitelist (allow only programs to run if explicitly enabled).
By default, most administrators use path rules to enable whole folders (c:\program files etc.), but with GoToWebinar (or Launcher), this is hardly possible because it extracts files to %LOCALAPPDATA%\Temp with random file and folder names.
It is definitely not a good idea to allow the whole Temp folder to execute files!
Solution for Webinar:
As stated here, instead of a path rule, use a certificate rule in your GPO settings.
You get the certificate if you select e.g. your “GoToWebinar Launcher.exe” instead of any .cer or .crt file. It will extract the certificate automatically, so you get a new rule in your whitelist. After doing a “gpupdate /force” on the workstation (or re-login), users should be able to start the Webinar application.
Note: Make sure you have configured your GPO to also process (enforce) certificate rules! (Enforcement object)