Dtd Prohibited in Xml Document Exception

DTD prohibited in xml document exception

Note that settings.ProhibitDtd is now obsolete, use DtdProcessing instead: (new options of Ignore, Parse, or Prohibit)

XmlReaderSettings settings = new XmlReaderSettings();
settings.DtdProcessing = DtdProcessing.Parse;

and as stated in this post: How does the billion laughs XML DoS attack work?

you should add a limit to the number of characters to avoid DoS attacks:

XmlReaderSettings settings = new XmlReaderSettings();
settings.DtdProcessing = DtdProcessing.Parse;
settings.MaxCharactersFromEntities = 1024;

DTD is prohibited exception when transforming XML file

If the XSLT uses or references a DTD, pass an XmlReader with the necessary XmlReaderSettings to the Load method, i.e. use the overload https://learn.microsoft.com/en-us/dotnet/api/system.xml.xsl.xslcompiledtransform.load?view=netframework-4.8#System_Xml_Xsl_XslCompiledTransform_Load_System_Xml_XmlReader_ with

using (XmlReader xsltReader = XmlReader.Create(xsltPath, new XmlReaderSettings() { DtdProcessing = DtdProcessing.Parse }))
{
  transformObj.Load(xsltReader);
}

DTD is prohibited in this XML document

You shouldn't download the schema from the server every time your program runs. You should download it once and keep it on your hard drive.

I think this will also take care of the “protocol violation” error.

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