It’s a common problem.
Hyperextension of the lumbar spine.
Lordosis
Anterior Pelvic tilt, as @manuelp2 mentioned.
Alan Thrall about fixing Anterior Pelvic Tilt.
Really short. Proper position in a squat.
And there’s some advice here.
Anterior Pelvic Tilt Problem
You’ll find lots of videos about the dangers of Over Extension or Hyperextension of the low back during the DL, Squat, or OHP.
Also, lots of general videos about how to fix lordosis or anterior pelvic tilt.
Work on your posture in your regular life, AND be vigilant about keeping your back in the proper position when you lift.