You will most likely gain some fat when bulking. In order to gain muscle you have to eat more calories than you burn and doing so can lead to some fat gain. Some people try to stay shredded while gaining muscle by either not eating enough calories or doing too much cardio . Doing so may allow them to stay super lean but they won't be gaining much muscle. At the other end of the spectrum some people eat everything in sight to get as many calories as they can. This strategy will definitely lead to weight gain, but a lot of that weight will be fat and not muscle. The best approach is to eat sufficient calories to gain muscle but don't get crazy with your eating and still doing some cardio to maintain cardiovascular health.