For example just try to write the following line and you will get rejected for suspicious input:

<code><head></code>

Comments

Steven’s picture

Steven commented
Priority: Critical » Normal
Status: Active » Closed (won't fix)

This is the Drupal XSS filter, not codefilter.module doing this. The XSS filter has been rewritten for 4.7 though and no longer aborts the request incorrectly.