What's showing up is the outline. The outline is a CSS property. It appears on elements that are in focus (such as an input being typed in). You can remove it if you like, but make sure to use border, box-shadow, or something else when it is focused. Adding a focus indicator is important for web accessibility. Here's an example of what is happening and a possible solution:
input {
border-radius: 10px;
}
#input2 {
  outline: none;
}
#input2:focus {
  border: 2px solid blue;
}
<input id="input1">
<br><br>
<input id="input2">
 
 
This substitutes border for outline. It's still accessible, but border respects border-radius.