.skylight-dialog {
    width: 50%;
    height: 400px;
    position: fixed;
    top: 50%;
    left: 50%;
    margin-top: -200px;
    margin-left: -25%;
    background-color: #fff;
    border-radius: 2px;
    z-index: 100;
    padding: 10px;
    box-shadow: 0 0 4px rgba(0,0,0,.14),0 4px 8px rgba(0,0,0,.28);
}

.skylight-dialog--close {
    cursor: pointer;
    float: right;
    font-size: 1.6em;
}

.skylight-dialog__overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 99;
    background-color: rgba(0,0,0,0.3);
}
.skylight-dialog {
    width: 50%;
    height: 400px;
    position: fixed;
    top: 50%;
    left: 50%;
    margin-top: -200px;
    margin-left: -25%;
    background-color: #fff;
    border-radius: 2px;
    z-index: 100;
    padding: 10px;
    box-shadow: 0 0 4px rgba(0,0,0,.14),0 4px 8px rgba(0,0,0,.28);
    overflow: auto;
}

.skylight-dialog--close {
    cursor: pointer;
    float: right;
    font-size: 1.6em;
}

.skylight-dialog__overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 99;
    background-color: rgba(0,0,0,0.3);
}
Apply overflow on Skylight modal
Apply overflow on Skylight modal

Its content can be larger than its bounds so it's better to use overflow
here.
