diff --git a/tests/unit/test_form.py b/tests/unit/test_form.py
index 6f5de573c..68223f7a5 100644
--- a/tests/unit/test_form.py
+++ b/tests/unit/test_form.py
@@ -6,6 +6,7 @@
 import json
 import unittest
 
+import pytest
 from werkzeug.datastructures import MultiDict
 
 import webcompat
@@ -321,5 +322,18 @@ def test_report_issue_anonymous_fails_with_wrong_credentials(self):
             self.assertEqual(rv.status_code, 400)
 
 
+@pytest.mark.parametrize(
+    'test_input,expected',
+    [({}, 'web'),
+     ({'src': ''}, 'unknown'),
+     ({'src': 'punkCat'}, 'unknown'),
+     ({'src': 'mobile-reporter'}, 'mobile-reporter'),
+     ]
+)
+def test_report_source(test_input, expected):
+    """Extract the reporting source when valid and invalid."""
+    assert form.extract_report_source(test_input) == expected
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/webcompat/form.py b/webcompat/form.py
index 06e84a4a2..17d0f04c6 100644
--- a/webcompat/form.py
+++ b/webcompat/form.py
@@ -294,7 +294,7 @@ def get_form(form_data, form=IssueForm):
     bug_form.details.data = json.dumps(form_data.get('details'), indent=2)
     bug_form.extra_labels = form_data.get('extra_labels', None)
     bug_form.os.data = get_os(ua_header)
-    bug_form.reported_with.data = form_data.get('src', 'web')
+    bug_form.reported_with.data = extract_report_source(form_data)
     bug_form.ua_header.data = ua_header
     bug_form.url.data = form_data.get('url', None)
     return bug_form
@@ -443,6 +443,28 @@ def add_metadata(form, metadata_dict):
     return form
 
 
+def extract_report_source(form_data):
+    """Extract the source of report.
+
+    This also controls if the src argument is part of a known list.
+    """
+    reported_with = 'unknown'
+    try:
+        reported_with = form_data['src']
+        if not is_valid_source(reported_with):
+            reported_with = 'unknown'
+    except KeyError:
+        reported_with = 'web'
+    return reported_with
+
+
+def is_valid_source(reported_with):
+    """Only a known subset of known values are accepted."""
+    if reported_with in app.config['REPORTED_WITH']:
+        return True
+    return False
+
+
 def build_formdata(form_object):
     """Convert HTML form data to GitHub API data.