For a spontaneous reaction, $∆\mathrm{G}<0.$

As per the Gibbs-Helmholtz equation,

$∆\mathrm{G}=∆\mathrm{H}-\mathrm{T}∆\mathrm{S}$

When $∆\mathrm{H}$ is negative, i.e., the reaction is exothermic and $∆\mathrm{S}$ is positive, i.e., the disorder is increasing, the value of $∆\mathrm{G}$ will definitely be negative and the process will be spontaneous for all temperatures.