Dtd-is-prohibited-error-when-accessing-sharepoint-2013-office365-list-but-not

Question

I need to update some items in a list and previously done it through a console app and using the sharepoint.client.dll but for some reason it no longer works. 
When I call the clientContext.ExecuteQuery() it throws this error:-
"For security reasons DTD is prohibited in this XML document. To enable DTD processing set the DtdProcessing property on XmlReaderSettings to Parse and pass the settings into XmlReader.Create method."
I have googled this and seen others have had similar problems but changing DNS has not resolved this which did in their case.
I can probably create a sharepoint-hosted app to do it but just takes longer for such a simple update.
I have checked fiddler and can see it is requesting the FPUrl.xml and returning a 302 response.
GET http://msoid.thesportsoffice.com/FPUrl.xml HTTP/1.1
Host: msoid.thesportsoffice.com
HTTP/1.1 302 Found
Cache-Control: private
Content-Type: text/html; charset=utf-8
Location: /
Server: Microsoft-IIS/8.5
X-AspNetMvc-Version: 4.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Fri, 26 Sep 2014 14:43:36 GMT
Content-Length: 118
Any ideas why this is starting to happen?
Karl Diggle

Answer 1

Hi D00gle,
DTD means document type declaration. Using DTD entity expansion, it is easy to make a very small XML data stream fully expand into a very large document.
It will run parser without source limit, so the system will tell you the data has a security issue.
To fix the issue, you can set like below in your code:
XmlReaderSettings settings = new XmlReaderSettings();
settings.ProhibitDtd = false;
Here is a thread about this issue for your reference:
http://stackoverflow.com/questions/13854068/dtd-prohibited-in-xml-document-exception
Feel free to reply if you still have any questions about this.
Best Regards
TechNet Community Support
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