A vulnerability was found in Moodle where javaScript injection was possible in some Mustache templates via recursive rendering from contexts. Mustache helper tags that were included in template contexts were not being escaped before that context was injected into another Mustache helper, which could result in script injection in some templates. This affects versions 3.7 to 3.7.1, 3.6 to 3.6.5, 3.5 to 3.5.7 and earlier unsupported versions.