The person who installed my frameless shower glass mounted two brackets directly into the shower curb. There is some silicone visible around the brackets... I'm not sure if silicone was used in the screw holes.
The curb is made of quartz composite and the waterproofing underneath is hot mop.
The glass was over a year ago, and I haven't seen signs of moisture damage yet, but it does concern me. Is this a big problem?
Edit: Here is a photo of one of the brackets