Abnormal sign/pixel in dock after 15.1.1 update

I just updated to MacOS 15.1.1 and an abnormal sign/pixel appeared on the right side of the dock after the last application. It's not a screen problem because, for example, by logging out and having only the desktop background, the sign disappears. Furthermore, by moving the dock to the left or right of the screen the sign remains in the same position. Have you noticed it too? For me, since I'm picky, this is a very annoying problem. How do I report this to Apple? Thank you