[Vuejs]-Firebase hosting changes an element's opacity to 1% whenever it has CSS opacity

This sounds like a common problem people run across when using Sass.

Percentages in Sass work just like every other unit. They are not
interchangeable with decimals, because in CSS decimals and percentages
mean different things. For example, 50% is a number with % as its
unit, and Sass considers it different than the number 0.5.

Instead of using percentages in your CSS, change them to the equivalent decimal representation.

For example, use opacity: 0.8; instead of opacity: 80%;