We investigate the unsteadiness generated by an oblique shock impinging on a laminar Mach 5.92 boundary layer. Previous investigations found that a M = 2.15 boundary layer undergoes a three-dimensional bifurcation to linear instability. Using the US3D hypersonic flow solver, we investigate whether this bifurcation remains three- dimensional in the case of an oblique shock impinging on a laminar hypersonic boundary layer with M = 5.92. We characterize the frequency and spanwise wavenumber selected by this bifurcation using direct numerical simulation (DNS), sparsity-promoting dynamic mode decomposition (SPDMD), and global stability analysis. DNS reveals that the hypersonic boundary remains laminar for an oblique shock angle of θ = 12°, but becomes unstable and transitions to turbulence once the shock angle increases to θ = 14°. In this case, spanwise Fourier velocity spectra and SPDMD of the DNS data show that the flow selects a particular spanwise wavenumber and frequency. We confirm this frequency and wavelength via global stability analysis about steady two-dimensional baseows obtained from DNS.