Today we released a security patch for Laravel 6.x and 7.x. In previous releases of Laravel, it was possible to mass assign Eloquent attributes that included the model's table name: When doing so, Eloquent would remove the table name from the attribute for you. This was a "convenience" feature of Eloquent and was not documented.
For this reason, we have removed the automatic stripping of table names from mass-asignment operations so that the attributes go through the typical "fillable" / "guarded" logic.
Since this feature was relatively unknown and undocumented, we expect the vast majority of Laravel applications to be able to upgrade without issues.