It's the A-arm. Stop driving the car until it's fixed... or else.
Before mine went at the track, I was getting a hard pull right under braking. One of the welds on the LCA had failed, allowing the other to flex toeing the left tire in and turning the car right. I noticed the issue and checked the car out in the pits but couldn't see the failure when the car was static... it only took like 3 more slow laps and then it failed completely. I was lucky to be at a race track with runoff and at only around 40mph when it let go... if it had occurred on the street, or on the freeway heading home, it would have been a huge mess.