Created guide on customizing these queries, and referenced it in the query help

Author: aegilops

javascript/ql/src/Security/CWE-830/CUSTOMIZING.md

@@ -0,0 +1,43 @@
+# Functionaility from untrusted source/domain - customizations
+
+You can extend the behavior of the `js/functionality-from-untrusted-source` and `js/functionality-from-untrusted-domain` queries using [CodeQL data extensions](https://codeql.github.com/docs/codeql-language-guides/customizing-library-models-for-javascript/).
+
+This allows you to require Subresource Integrity (SRI) checks on specific content delivery network (CDN) hostnames, and add additional domains to warn on, respectively.
+
+For example, this YAML model can be used inside a CodeQL model pack to alert on uses of `example.com` in imported functionality, extending the `js/functionality-from-untrusted-domain` query:
+
+```yaml
+extensions:
+  - addsTo:
+      pack: codeql/javascript-all
+      extensible: untrustedDomain
+    data:
+      - ["example.com"]
+```
+
+To add new hostnames that always require SRI checking, this YAML model can be used to require SRI on `cdn.example.com`, extending the `js/functionality-from-untrusted-source` query:
+
+```yaml
+extensions:
+  - addsTo:
+      pack: codeql/javascript-all
+      extensible: isCdnDomainWithCheckingRequired
+    data:
+      - ["cdn.example.com"]
+```
+
+A suitable [model pack](https://docs.github.com/en/code-security/codeql-cli/using-the-advanced-functionality-of-the-codeql-cli/creating-and-working-with-codeql-packs#creating-a-codeql-model-pack) might be:
+
+```yaml
+name: my-org/javascript-untrusted-functionality-model-pack
+version: 1.0.0
+extensionTargets:
+  codeql/java-all: '*'
+dataExtensions:
+  - models/**/*.yml
+```
+
+## References
+
+- [Customizing library models for javascript](https://codeql.github.com/docs/codeql-language-guides/customizing-library-models-for-javascript/)
+- [Creating and working with CodeQL packs](https://docs.github.com/en/code-security/codeql-cli/using-the-advanced-functionality-of-the-codeql-cli/creating-and-working-with-codeql-packs#creating-a-codeql-model-pack)

javascript/ql/src/Security/CWE-830/FunctionalityFromUntrustedDomain.qhelp

@@ -32,6 +32,10 @@
 		<p>
 			Even when <code>https</code> is used, an untrustworthy operator might deliver malware.
 		</p>
+
+		<p>
+			See the `CUSTOMIZING.md` file in the source code for this query for information on how to extend the list of untrusted domains used by this query.
+		</p>
 	</overview>
 
 	<recommendation>