in src/main/java/org/apache/sling/auth/form/impl/FormAuthenticationHandler.java [737:741]
public CookieStorage(final String cookieName, final String defaultCookieDomain) {
this.cookieName = cookieName;
this.domainCookieName = cookieName + "." + COOKIE_DOMAIN;
this.defaultCookieDomain = defaultCookieDomain;
}