Potassium iodide acts as a reducing agent when treated with 

KI is reducing agent $2I^{-}\to I_2+2e$and$C{r}_2{O}_7^{2-}/H^{+}Mn{O}_4^{+}/H^{+}andC{u}^{2+}$are  all oxidizing agents. SO  $I^{-}$ reduces them, and is it self oxidized.