# documentación de Django - 5.2.8

# Django 1.4.20 release notes

March 18, 2015

Django 1.4.20 fixes one security issue in 1.4.19.

## Mitigated possible XSS attack via user-supplied redirect URLs

Django relies on user input in some cases (e.g. `django.contrib.auth.views.login()` and i18n) to redirect the user to an «on success» URL. The security checks for these redirects (namely `django.utils.http.is_safe_url()`) accepted URLs with leading control characters and so considered URLs like `\x08javascript:...` safe. This issue doesn’t affect Django currently, since we only put this URL into the `Location` response header and browsers seem to ignore JavaScript there. Browsers we tested also treat URLs prefixed with control characters such as `%08//example.com` as relative paths so redirection to an unsafe target isn’t a problem either.

However, if a developer relies on `is_safe_url()` to provide safe redirect targets and puts such a URL into a link, they could suffer from an XSS attack as some browsers such as Google Chrome ignore control characters at the start of a URL in an anchor `href`.