Through a malicious URL that contained a quote character it was possible to inject HTML code in KMail's plaintext viewer. Due to the parser used on the URL it was not possible to include the equal sign (=) or a space into the injected HTML, which greatly reduces the available HTML functionality. Although it is possible to include an HTML comment indicator to hide content.

References

• https://nvd.nist.gov/vuln/detail/CVE-2016-7966
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QNMM5TVPTJQFPJ3YDF4DPXDFW3GQLWLY/
• http://lists.opensuse.org/opensuse-updates/2016-10/msg00065.html
• http://www.debian.org/security/2016/dsa-3697
• http://www.openwall.com/lists/oss-security/2016/10/05/1
• http://www.securityfocus.com/bid/93360