iOS 7 - No circles around 'Enter passcode' numbers.

What wallpaper are you using for the lock screen? Is it by any chance black?

I think those circles are "translucent" and show a diffuse glimpse of the wallpaper "beneath" the passcode screen. For example, my lock screen is a photo of a bush in my back yard; the bottom two rows of large circles are in greens and blues, the top row is yellowish where my house "shows through", and the bottom large circle around the zero and the small circles at the top are pale gray.

it really shouldn't matter what colour your background is, i always use a black one and i had the same problem when updating to ios7 originally. it eventually went away but after another update to ios 7.0.6 the problem is back.

i found i could always "fix" it by swiping up the control centre and adjusting the brightness (didn't matter what brightness, just as long as you adjusted which ever way). but whenever the phone locks the circle's dissappear again.

maybe it'll go away on it's own again..

Well, whether it should or shouldn't matter, the background color does seem to matter if you have translucent circles.

Mate,

Autobirghtness on should fix the issue. When autobrightness is off you wont see the circles. Hope this helps. Worked for me.