The most likely cause is that the viewfinder diopter adjustment has been moved. The diopter controls how the viewfinder display looks to your eye, including the AF points and exposure information. If it’s out of adjustment, those markings can appear blurry even though the camera itself is fine.

To fix it, look through the viewfinder and turn the diopter adjustment wheel next to the eyepiece until the focus points and viewfinder information appear sharp. Half-press the shutter if needed so the display lights up while you adjust it.

This is unrelated to having no lens attached—the blur is usually just a viewfinder eyesight adjustment issue, not a focusing problem with the camera.