Error 403: Unable to post this reply (see txt file in ZIP)

[frm]

Cannot seem to post this text from reply.txt in the attached zip.

In any message (new thread, etc.), I get a 403 response.

 

[frm]

Looks like it comes down to the script tag. Anything in a script tag, even if in a code block, won't post, but other tags will, whether inside a code block or not.

How it can be typed (but not rendered):
< script >

<html>

<html>

Seems like it might be a CloudFlare issue as seen in this bug report:

Closed Thread 'Option explanation field script tag breaks options page (Save button disappears)'

Jun 12, 2026

Location: Admin CP > Setup > Options > Create or Edit option > Explanation field

The Explanation field on the option edit page shows the label "You may use HTML". However, if the explanation text contains a <script> tag (for example, when documenting that an option outputs a <script type="application/ld+json"> block in the page head), the tag is rendered raw into the Admin CP options page. This causes the page to stop rendering correctly, and the Save button at the bottom of the options group page disappears entirely.

This is...

• Eris Greyrat
• Replies: 3
• Forum: Resolved bug reports

 

[Chromaniac]

xenforo has a plain text bbcode. though not sure if it would help here assuming this is a server side safety thing?

BB codes

The list of BB codes you can use to spice up the look of your messages. This page shows a list of all BB codes that are available.

xenforo.com

 

[frm]

xenforo has a plain text bbcode. though not sure if it would help here assuming this is a server side safety thing?

BB codes

The list of BB codes you can use to spice up the look of your messages. This page shows a list of all BB codes that are available.

xenforo.com

Doesn't matter if you wrap it in PLAIN, either.

It'll be a 403 with this error:
Oops! We ran into some problems. Please try again later. More error details may be in the browser console.

You can replicate it by copy/pasting it over here and clicking the Preview or Reply button.

<script> HTML script element - HTML | MDN

The <script> HTML element is used to embed executable code or data; this is typically used to embed or refer to JavaScript code. The <script> element can also be used with other languages, such as WebGL's GLSL shader programming language and JSON.

developer.mozilla.org

 

[Xon]

This sort of thing is a clouldflare configuration issue, not really an XF bug.

You can trigger this sort of thing when editing templates in the admincp semi-frequently.