The two-dimensional (zero magnetic field) Ising model is known to undergo a second-order paraferromagnetic phase transition, which is accompanied by a correlated percolation transition for the Fortuin-Kasteleyn (FK) clusters. In this paper we uncover that there exists also a second temperature
Teb<Tc at which the elastic backbone of FK clusters undergoes a second-order phase transition to a dense phase. The corresponding universality class, which is characterized by determining various percolation exponents, is shown to be completely different from directed percolation, which leads us to propose a new anisotropic universality class with $\ensuremath{\beta}=0.54\ifmmode\pm\else\textpm\fi{}0.02$, ${\ensuremath{\nu}}_{||}=1.86\ifmmode\pm\else\textpm\fi{}0.01$, ${\ensuremath{\nu}}_{\ensuremath{\perp}}=1.21\ifmmode\pm\else\textpm\fi{}0.04$, and ${d}_{f}=1.53\ifmmode\pm\else\textpm\fi{}0.03$. All tested hyperscaling relations are shown to be valid.