ASA-2018-00011 – Squid: Cross-Site Scripting issue in TLS error processing

Due to incorrect input handling, Squid is vulnerable to a Cross-Site Scripting vulnerability when generating HTTPS response messages about TLS errors. Several fields of X.509 certificates can contain HTML syntax and were not being correctly quoted/encoded before inserting into HTML error pages generated by the proxy. This issue allows an attacker to craft a X.509 certificate that both triggers an error and alters how that error is displayed by a client such as a Browser.