You may see this kind of alert if a Symantec product determined that the file has a "low reputation". This may happen especially for new versions that have been released just recently.

The downloaded file is quarantined immediately, preventing you from installing the software.

Please read this article on how to restore the file from quarantine:
Clarification on WS.Reputation.1 detection

If you want to be sure, you can submit the file to online virus scanners, where it will be checked by a number of different anti-virus products:

If possible, you can submit the file to your anti-virus vendor, so they will analyse and whitelist it if needed.