Ghost/ghost/admin/app/styles/layouts/auth.css

/* Sign in
/* ---------------------------------------------------------- */

.gh-signin {
    position: relative;
    margin: 30px auto;
    padding: 40px;
    max-width: 400px;
    width: 100%;
    border: #dae1e3 1px solid;
    background: #f8fbfd;
    border-radius: 5px;
    text-align: left;
}

.gh-signin .form-group {
    margin-bottom: 1.5rem;
}

.gh-signin .btn {
    margin: 0;
    padding: 12px;
}

.forgotten-wrap {
    position: relative;
}

.forgotten-wrap input {
    padding-right: 7rem;
}

.forgotten-wrap .forgotten-link {
    position: absolute;
    top: 10px;
    right: 1px;
    bottom: 10px;
    padding: 0 11px 0 12px;
    border-left: #dae1e3 1px solid;
    border-radius: 0;
    text-transform: none;
    letter-spacing: 0;
    font-size: 1.1rem;
    line-height: 1.2rem;
}

.forgotten-link:hover {
    border-left: #dae1e3 1px solid;
    color: color(var(--blue) lightness(-20%));
    text-decoration: none;
}

.forgotten-link:active {
    box-shadow: none;
    text-decoration: underline;
}