There is not a bug present here. The issue arises from setting the wrapper to 300px and applying the overflow property of hidden, which allows for scrolling if the content exceeds the defined width. I am currently using Firefox on OSX and can confirm that scrolling is possible within the container.
To potentially resolve this, you may need to implement the following code within the text field HTML markup:
onmousedown="event.preventDefault ? event.preventDefault() : event.returnValue = false; this.focus()"
This code snippet should prevent users from dragging inside the box when selected, but keep in mind it also disables clicking within the box. You would need to manually focus on the box if this behavior aligns with your intended functionality.