Depends on what you need it for. For example for a network with 3 computers and no internet connection, for only printing and accessing files shouldn't be a security problem. If you have a big and complex network with internet and very important files on servers/clients then yes, v1 is security risk.
fg.ds.b1.download.windowsupdate.com/c/Upgr/2018/09/17763.1.180914-1434.rs5_release_clientconsumer_ret_x64fre_en-us_a21ecd9defb6c71439dc7bbf6bc3684be8fd9aea.esd
The final ISO images are ready and hosted on Microsoft servers. Today they can be downloaded through the MCT.
Patience is a virtue, a few weeks from now everything will be wide open available to everyone. If people is desperate for 1809 RS5 there are ESD files available that can easily be converted to ISO. 3 weeks equals roughly 504 hours, and that's what I think is the max you have to wait for everything you need including LTSC. Just grab some and enjoy what you have right now.
Why you gotta be rude? I was just stating that MCT is still 1803 I have already installed by converting the ESD to ISO