diff --git a/guarddog/analyzer/metadata/npm/__init__.py b/guarddog/analyzer/metadata/npm/__init__.py
index 2347a128..4b6c485a 100644
--- a/guarddog/analyzer/metadata/npm/__init__.py
+++ b/guarddog/analyzer/metadata/npm/__init__.py
@@ -7,6 +7,7 @@
 from guarddog.analyzer.metadata.npm.direct_url_dependency import (
     NPMDirectURLDependencyDetector,
 )
+from guarddog.analyzer.metadata.npm.npm_metadata_mismatch import NPMMetadataMismatch
 
 NPM_METADATA_RULES = {}
 
@@ -16,6 +17,7 @@
     NPMPotentiallyCompromisedEmailDomainDetector,
     NPMTyposquatDetector,
     NPMDirectURLDependencyDetector,
+    NPMMetadataMismatch,
 ]
 
 for detectorClass in classes:
diff --git a/guarddog/analyzer/metadata/npm/npm_metadata_mismatch.py b/guarddog/analyzer/metadata/npm/npm_metadata_mismatch.py
new file mode 100644
index 00000000..872c2281
--- /dev/null
+++ b/guarddog/analyzer/metadata/npm/npm_metadata_mismatch.py
@@ -0,0 +1,101 @@
+from typing import Optional, Any, Union, get_args
+from pathlib import Path
+import json
+
+from guarddog.analyzer.metadata.detector import Detector
+
+# List of fields where mismatch between package.json and NPM can carry malicious information
+# (field, expected type)
+MANIFEST_FIELDS_CHECKLIST = {
+    "dependencies": dict, 
+    "devDependencies": dict, 
+    "scripts": dict,
+    "main": str, 
+    "repository": dict, 
+    "bugs": dict, 
+    "homepage": str
+}
+
+class NPMMetadataMismatch(Detector):
+    def __init__(self):
+        super().__init__(
+            name="npm_metadata_mismatch",
+            description="Identify packages which have mismatches between the npm pacakge manifest and the package info"
+        )
+
+    def detect(self, package_info, path: Optional[str] = None, name: Optional[str] = None,
+               version: Optional[str] = None) -> tuple[bool, Optional[str]]:
+        # Get the latest version if not specified
+        if not version:
+            version = package_info["dist-tags"]["latest"]
+
+        # Load package.json manifest
+        if path is None:
+            raise ValueError("path is needed to run heuristic " + self.get_name())
+        package_json = Path(path) / "package" / "package.json"
+        package_manifest: dict[Any] = json.loads(package_json.read_text())
+
+        # Get NPM manifest for version
+        version_info = package_info["versions"][version] 
+
+        diff: list[Diff] = {
+            field: difference_at_key(version_info, package_manifest, field, field_type)
+            for field, field_type in MANIFEST_FIELDS_CHECKLIST.items()
+        }
+        number_different = sum(len(v) for k,v in diff.items())
+        diff_description = describe_diff(diff) if number_different != 0 else "No differences found"
+        return number_different != 0, diff_description
+
+PerItemDiff = tuple[str,str,str]
+Diff = list[PerItemDiff] 
+
+def diff_at_key_dict(version_at_key: dict[Any], manifest_at_key: dict[Any]) -> Diff:
+    return [
+        (key, version_at_key.get(key), manifest_at_key.get(key))
+        for key in set(version_at_key.keys()).union(set(manifest_at_key.keys())) 
+        if version_at_key.get(key) != manifest_at_key.get(key)
+    ]
+
+def difference_at_key(version_info: dict[Any], package_manifest: dict[Any], key: str, key_type) -> Diff:
+    version_at_key = version_info.get(key, key_type())
+    manifest_at_key = package_manifest.get(key, key_type())
+    if not(isinstance(version_at_key, key_type) and isinstance(manifest_at_key, key_type)):
+        return [(f"Expected type {str(key_type)}", f"{type(version_at_key)}", f"{type(manifest_at_key)}")]
+    elif key_type == dict:
+        return diff_at_key_dict(version_at_key, manifest_at_key)
+    else:
+        # If it is not a dict do a direct comparison of the value at the key, currently the only other type is strings
+        return [(f"{key}", version_at_key, manifest_at_key)] if version_at_key != manifest_at_key else []
+
+
+def describe_diff(diff: Diff) -> str:
+    """
+    Creates a string of the form 
+    Difference between manifest and package.json found:
+    dependencies:
+        key: Manifest("v4.0.0"), package.json("v3.0.1")
+    scripts:
+        key: Manifest("a"), package.json("b")
+    main:
+        Manifest:
+            index.js
+        package.json
+            malicious.js
+    ...
+    """
+    description = "Difference between manifest and package.json found: \n"
+    for k, differences in diff.items():
+        if differences:
+            field_description = f"{k}: \n"
+            if MANIFEST_FIELDS_CHECKLIST[k] == dict:
+                for d in differences:
+                    field_description += f"  {d[0]}: Manifest(\"{d[1]}\"), package.json(\"{d[2]}\") \n"
+            else:
+                manifest_str = "  Manifest:\n"
+                package_str = "  package.json:\n"
+                for d in differences:
+                    manifest_str += f"    {d[1]}\n"
+                    package_str += f"    {d[2]}\n"
+                field_description = field_description + manifest_str + package_str
+            description += field_description
+    return description