Cosmic strings are formed due to topological defects during symmetry breaking phase transition in early universe.
While Goldstone theorem states whenever we have continuous symmetry and it is spontaneously broken then we have scalar particles appearing in spectrum of excitation.
I'm wondering if these concept have any correlation? Also as I have marked we should have a spontaneous symmetry breaking for Goldstone theorem to hold but wiki article doesn't state whether cosmic strings have to be formed during spontaneous symmetry breaking.