Even worse in front of the cylinder of a black powder revolver, especially if the chambers are filled with grease after loading. A flashback could fire additional chambers. Main reason the Colt revolving rifle was not popular.
Back in the '60s my younger brother (15) and I were out shooting in the woods, near dusk. He had a habit of laying the handgun across his left forearm "for support" when shooting. I told him that was a big no-no with revolvers.
We were shooting an old Starr single action cap and ball revolver. Luckily, he didn't use his "support" method but held it in the normal fashion - and fired a shot. The forest lit up as adjacent rounds fired due to the flashback you mentioned. His eyes were as big as saucers and the lesson sunk in. (Big brother wasn't as dumb as he looked.)