curl - security update

It was discovered that cURL, an URL transfer library, if configured to
use a proxy server with the HTTPS protocol, by default could send to the
proxy the same HTTP headers it sends to the destination server, possibly
leaking sensitive information.

For the stable distribution (jessie), this problem has been fixed in
version 7.38.0-4+deb8u2.

For the testing distribution (stretch), this problem will be fixed in
version 7.42.1-1.

For the unstable distribution (sid), this problem has been fixed in
version 7.42.1-1.

We recommend that you upgrade your curl packages.