Comment 1 for bug 31589

If I go to https://launchpad.net/+login, the template code puts the following in the form element:

    <input type="hidden" name="redirection_url" />

So the redirection_url form item will be posted back with a value of "".

If I go to https://launchpad.net/+login?redirction_url= (essentially what I'd get for posting an empty redirection_url), The form contains the following:

    <input type="hidden" name="redirection_url" />
    ...
    <!-- Preserve extra query parameters as hidden fields. -->
    <input type="hidden" name="redirection_url" value="" />

This would result in two "redirection_url" items being posted back, which is similar to the results observed in the OOPS.