Cabrera led off the 10th with a walk off Jonathan Papelbon (2-4) and went to third on Buster Posey's single.
He took off for the plate as Blanco squared to bunt and crossed the plate with the go-ahead run after the Giants outfielder executed the play -- two innings after he missed a sign on another squeeze try that saw Posey cut down at the plate.
Sergio Romo (3-1) was credited with the win after getting the final two outs in the ninth and Santiago Casilla racked up his 24th save in the victory, which clinched the three-game series for the National League West-leading Giants.
Posey finished 3-for-4 with a two-run homer and three RBI, while Cabrera and pitcher Matt Cain also went deep for San Francisco.
Phillies starter Cole Hamels socked his first career homer but yielded five runs on 10 hits over 7 2/3 innings.