Top panels: CMDs of the initial sample with the No. 592 indicated. It is shown that the No. 592 is the reddest target in our sample. An additional check without the K_S-band magnitude constrain (K_S≤ 12.5 mag; Sect. 4.1) also shows that this target is the reddest object detected by WISE and Spitzer. Bottom left: Enhanced IRS spectrum of ∼ 5–14 µm. Bottom right: MIR lightcurves of WISE1 and WISE2 bands. See text for details.