Steps to replicate the issue (include links if applicable):
- Load the 'Get users' result with an IP
- Try to use the block form
- The form does not submit
Software version (skip for WMF-hosted wikis like Wikipedia):
Checkuser on the master branch
Other information (browser name/version, screenshots, etc.):
Latest Firefox
This fails because the paging links which are added on the get users screen use a form element to ensure that the data is sent via POST. The HTML spec says that forms cannot be nested, so at least in Firefox the form element is ignored. The quickest fix for this is to remove the paging links at the bottom, but an alternative is for non-IE browsers use the HTML form attribute on the checkboxes so that the bottom paging links can be shown on non-IE browsers. IE browsers do not support this attribute so some browser detection would be needed.