In Moodle 3.x, the setting for blocked hosts list can be bypassed with multiple A record hostnames.
{
"versions": [
{
"introduced": "0"
},
{
"last_affected": "3.2.0"
},
{
"introduced": "0"
},
{
"last_affected": "3.2.1"
},
{
"introduced": "0"
},
{
"last_affected": "3.2.2"
},
{
"introduced": "0"
},
{
"last_affected": "3.2.3"
},
{
"introduced": "0"
},
{
"last_affected": "3.2.4"
},
{
"introduced": "0"
},
{
"last_affected": "3.2.5"
},
{
"introduced": "0"
},
{
"last_affected": "3.2.6"
},
{
"introduced": "0"
},
{
"last_affected": "3.3.0"
},
{
"introduced": "0"
},
{
"last_affected": "3.3.1"
},
{
"introduced": "0"
},
{
"last_affected": "3.3.2"
},
{
"introduced": "0"
},
{
"last_affected": "3.3.3"
},
{
"introduced": "0"
},
{
"last_affected": "3.4.0"
}
]
}