Add notes on security

1 files changed, 22 insertions, 0 deletions

diff --git a/README.md b/README.md
index 096772d..968d5e9 100644
--- a/README.md
+++ b/README.md
@@ -66,6 +66,10 @@ Install-Package Mammoth
 
 ### Library
 
+**Mammoth performs no sanitisation of the source document,
+and should therefore be used extremely carefully with untrusted user input.**
+See the [Security](#security) section for more information.
+
 #### Basic conversion
 
 To convert an existing .docx file to HTML,
@@ -299,6 +303,24 @@ var converter = new DocumentConverter()
 
 where `StreamToBase64` is a function that reads a stream and encodes it as a Base64 string.
 
+### Security
+
+Mammoth performs no sanitisation of the source document,
+and should therefore be used extremely carefully with untrusted user input.
+For instance:
+
+* Source documents can contain links with `javascript:` targets.
+  If, for instance, you allow users to upload source documents,
+  automatically convert the document into HTML,
+  and embed the HTML into your website without sanitisation,
+  this may create links that can execute arbitrary JavaScript when clicked.
+
+* Source documents may reference files outside of the source document.
+  If, for instance, you allow users to upload source documents to a server,
+  automatically convert the document into HTML on the server,
+  and embed the HTML into your website,
+  this may allow arbitrary files on the server to be read and exfiltrated.
+
 ## Writing style maps
 
 A style map is made up of a number of style mappings separated by new lines.