A flaw was discovered in mediawiki, a wiki engine: thumb.php outputs
wikitext messages as raw HTML, potentially leading to cross-site
scripting (XSS).
For the stable distribution (wheezy), this problem has been fixed in
version 1.19.20+dfsg-0+deb7u3; this version additionally fixes a
regression introduced in the previous release, DSA-3100-1.
For the upcoming stable distribution (jessie) and unstable
distribution (sid), this problem has been fixed in version
1:1.19.20+dfsg-2.2.
We recommend that you upgrade your mediawiki packages.