function handleLoginInOtherBrowserTab() {
  const currentUser = debiki2.ReactStore.getMe();
  const sessionId = getSetCookie('dwCoSid');
  if (currentUser.isLoggedIn) {
    if (sessionId) {
      // Session id example: (parts: hash, user id, name, login time, random value)
      // 'Y1pBlH7vY4JW9A.11.Magnus.1316266102779.15gl0p4xf7'
      const parts = sessionId.split('.');
      const newUserIdString = parts[1];
      if (currentUser.userId !== parseInt(newUserIdString)) {
        // We've logged in as another user in another browser tab.
        debiki2.ReactActions.loadMyself();
      }
    }
    else {
      const mainWin: MainWin = debiki2.getMainWin();
      if (mainWin.typs.weakSessionId) {
        // We're logged in, cookieless. Fine. [NOCOOKIES]
      }
      else {
        // We've logged out in another browser tab. The server should already know about this.
        debiki2.ReactActions.logoutClientSideOnly();
      }
    }
  }
  else if (sessionId) {
    // We've logged in in another browser tab.
    debiki2.ReactActions.loadMyself();
  }
}
According to WASC, "Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization."