CVE-2020-26956

Name	CVE-2020-26956
Description	In some cases, removing HTML elements during sanitization would keep existing SVG event handlers and therefore lead to XSS. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DLA-2457-1, DLA-2464-1, DSA-4793-1, DSA-4796-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
firefox (PTS)	sid	120.0-2	fixed
firefox-esr (PTS)	buster	91.12.0esr-1~deb10u1	fixed
	buster (security)	115.5.0esr-1~deb10u1	fixed
	bullseye	102.15.0esr-1~deb11u1	fixed
	bullseye (security)	115.5.0esr-1~deb11u1	fixed
	bookworm	102.15.1esr-1~deb12u1	fixed
	bookworm (security)	115.5.0esr-1~deb12u1	fixed
	sid, trixie	115.5.0esr-1	fixed
thunderbird (PTS)	buster	1:91.12.0-1~deb10u1	fixed
	buster (security)	1:115.5.0-1~deb10u1	fixed
	bullseye	1:102.13.1-1~deb11u1	fixed
	bullseye (security)	1:115.5.0-1~deb11u1	fixed
	bookworm	1:102.15.1-1~deb12u1	fixed
	bookworm (security)	1:115.5.0-1~deb12u1	fixed
	trixie	1:115.5.0-1	fixed
	sid	1:115.5.1-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Origin
firefox	source	(unstable)	83.0-1
firefox-esr	source	stretch	78.5.0esr-1~deb9u1	DLA-2457-1
firefox-esr	source	buster	78.5.0esr-1~deb10u1	DSA-4793-1
firefox-esr	source	(unstable)	78.5.0esr-1
thunderbird	source	stretch	1:78.5.0-1~deb9u1	DLA-2464-1
thunderbird	source	buster	1:78.5.0-1~deb10u1	DSA-4796-1
thunderbird	source	(unstable)	1:78.5.0-1

Notes

https://www.mozilla.org/en-US/security/advisories/mfsa2020-50/#CVE-2020-26956
https://www.mozilla.org/en-US/security/advisories/mfsa2020-51/#CVE-2020-26956
https://www.mozilla.org/en-US/security/advisories/mfsa2020-52/#CVE-2020-26956