Cuba is quite safe, relative to the Caribbean and other countries south of the US, in terms of violent crime. Gun crime is almost non-existent. However, as with most countries in the world, theft has been a problem for a hundred years. The bars are original to the house which make them 100 years old. If they're well-maintained, they prevent virtually any robbery from occurring through the window they protect.
I have a thread here where I post a lot of the going-ons in my neighbourhood. Recently, a neighbour had a 200 liter water tank stolen out of their patio! The thieves actually came by an hour earlier and entered the patio. We believe that they tipped the tank over to let it drain. When they returned, the same one hopped the wall and passed the tank to his accomplice. I'll post the video in a day or two.