Not sure if this is related to #946

From v1.12.6 onwards, cut.Find("iframe").GetAttribute("srcdoc") truncates src or srcdoc

<iframe srcdoc="@("<div style=\"margin: 10px\">aA Name</div>")"></iframe>

Assert.Equal(
    expected: "<div style=\"margin: 10px\">aA Name</div>",
    actual: cut.Find("iframe").GetAttribute("srcdoc")
);

Test fails from v1.12.6 onwards, outputting "<div style="