Template fails to save under strangely specific circumstances

[Neil-Clennan]

Description of the problem
I made edits to a template, but the template fails to save. When I click the "Save" button, I get the error:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at [email protected] to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.

The URL for the control panel page is /admin.php?/cp/design/template/edit/78

The strange thing is that failure or success seems to depend on the words included between paragraph tags. In one case, the text between the paragraph tags is "I want to move on." (without the quotation marks). Removing the word "on" allows it to be saved. This bug report won't let me paste in the code correctly, so I am attaching a screenshot. (Sorry for uploading twice; it was not clear that the first attempt was successful.)

I reproduced it again by doing the following:

1. Created a new HTML template
2. Typed the code into it as shown in the screenshot.
3. Clicked the save button.

Environment Details:

• Version: ExpressionEngine 6.4.11
• PHP Version 8.1.17
• MySQL Version 8.0.28-0ubuntu0.20.04.3
• OS: macOS
• Web Server: Apache

[intoeetive]

@Neil-Clennan this error does not seem to be coming from ExpressionEngine, so you probably need to talk to your hoster about that. Checking your server error log as advised in the message might be helpful

Initially it looks to me like some server software is considering POST request of saving template as something dangerous (something in the template looks suspicious to them).

Also, there's no screenshot attached )