In Joomla! before 3.9.19, the default settings of the global textfilter configuration do not block HTML inputs for Guest users.
{
"versions": [
{
"introduced": "2.5.1"
},
{
"fixed": "3.9.19"
},
{
"introduced": "0"
},
{
"last_affected": "2.5.0-NA"
},
{
"introduced": "0"
},
{
"last_affected": "2.5.0-beta1"
},
{
"introduced": "0"
},
{
"last_affected": "2.5.0-beta2"
},
{
"introduced": "0"
},
{
"last_affected": "2.5.0-rc1"
}
]
}