Nearly every fighting game has them, so it’s hardly a surprise that someone found an infinite combo string in Street Fighter IV. Thankfully, it’s very limited. Fei Long players fighting Seth or Abel can continually pull of a kick combo worthy of the Jeet Kun Do master himself. It should be noted that this is extremely difficult to pull on a continual basis and the videos online are done in the training mode.
While it’s sure to be fixed with a patch, the seemingly low number of Abel and Seth players online should be mildly careful until this is fixed. There’s always a small chance someone could pull this off and ruin your day.