govuk_tech_docs vulnerable to unescaped HTML on search results page

Impact

Pages that are indexed in search results have their entire contents
indexed, including any HTML code snippets. These HTML snippets would
appear in the search results unsanitised, so it was possible to
render arbitrary HTML or run arbitrary scripts.

This is a low risk security issue; to exploit it, an attacker would
need to find a way of committing malicious code to a page indexed
by a site that uses tech-docs-gem (which are typically not editable
by untrusted users). Their code would also be limited by the relatively
short length that’s rendered in the corresponding search result.
Nevertheless, the XSS would then be triggerable by visiting a
pre-constructed URL (/search/index.html?q=some+search+term), which
users could be tricked into clicking on through social engineering.

Patches

This has been fixed in v3.3.1. HTML is now sanitised in search results.