How to mask a password when creating a form

Site URL: http://www.wellroom.co.uk

Hi there,

I'm using Memberstack as to manage the membership of my site. 

I'm trying to create a custom login form, so basically, I create a form (just with username and password) on a page on my site, and then add memberstack's tags to the username and password bits in the code, to allow users to log into the site that way. 

I have managed to get it working, but I've noticed that because the 'password' box is just a regular Squarespace form text field, as the user types in their  password  the characters show up (instead of being replaced by dots or asterisks), which isn't great for security. 

Is there a way of changing this? What I'd like is if someone types their password for it to be masked with dots or asterisks. For example if someone types their password in and it's KermitTheFrog for the form to display ************ while they're typing. 

Thanks!

Rick