routinator -- Possible path traversal when storing RRDP responses

[email protected] reports:

NLnet Labs Routinator 0.9.0 up to and including 0.12.1 contains a
possible path traversal vulnerability in the optional, off-by-default
keep-rrdp-responses feature that allows users to store the content
of responses received for RRDP requests. The location of these
stored responses is constructed from the URL of the request. Due
to insufficient sanitation of the URL, it is possible for an attacker
to craft a URL that results in the response being stored outside
of the directory specified for it.