This vector uses an import inside a CSS string to test which characters cause an invalid CSS selector with a alpha prefix
<style>
x$[chr]{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div>window.getComputedStyle(x).color === 'rgb(255, 0, 0)' && log($[i])<style>
x0x01{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x02{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x03{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x04{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x05{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x06{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x07{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x08{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x0B{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x0E{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x0F{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x10{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x11{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x12{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x13{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x14{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x15{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x16{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x17{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div><style>
x0x18{position:"
}@import'data:text/css,%23x{color:red}';
</style>
<div id="x">test</div>