Security advisory PYSEC-2020-35: Django 1.11 before 1.11.28, 2.2 before 2.2.10, and 3.0 before 3.0.3 allows SQL Injection if untrusted data is used as a StringAgg delimiter (e.g., in Django applications that offer downloads of data as a series of rows with a user-specified column delimiter). By passing a suitably crafted delimiter to a contrib.postgres.aggregates.StringAgg instance, it was possible to break escaping and inject malicious SQL.
Package: django (pypi), vulnerable version: 3.0.2, fixed in: 3.0.3
Files changed by the fix:
django/contrib/postgres/aggregates/general.py
django/contrib/postgres/aggregates/mixins.py

Fix diff:
diff --git a/django/contrib/postgres/aggregates/general.py b/django/contrib/postgres/aggregates/general.py
index 918373e926e7..9616bc3e3e21 100644
--- a/django/contrib/postgres/aggregates/general.py
+++ b/django/contrib/postgres/aggregates/general.py
@@ -1,4 +1,5 @@
 from django.contrib.postgres.fields import ArrayField, JSONField
+from django.db.models import Value
 from django.db.models.aggregates import Aggregate
 
 from .mixins import OrderableAggMixin
@@ -51,11 +52,12 @@ def convert_value(self, value, expression, connection):
 
 class StringAgg(OrderableAggMixin, Aggregate):
     function = 'STRING_AGG'
-    template = "%(function)s(%(distinct)s%(expressions)s, '%(delimiter)s'%(ordering)s)"
+    template = '%(function)s(%(distinct)s%(expressions)s %(ordering)s)'
     allow_distinct = True
 
     def __init__(self, expression, delimiter, **extra):
-        super().__init__(expression, delimiter=delimiter, **extra)
+        delimiter_expr = Value(str(delimiter))
+        super().__init__(expression, delimiter_expr, **extra)
 
     def convert_value(self, value, expression, connection):
         if not value:
diff --git a/django/contrib/postgres/aggregates/mixins.py b/django/contrib/postgres/aggregates/mixins.py
index 3a43ca1a63ff..82e8eebdf4cf 100644
--- a/django/contrib/postgres/aggregates/mixins.py
+++ b/django/contrib/postgres/aggregates/mixins.py
@@ -3,7 +3,7 @@
 
 class OrderableAggMixin:
 
-    def __init__(self, expression, ordering=(), **extra):
+    def __init__(self, *expressions, ordering=(), **extra):
         if not isinstance(ordering, (list, tuple)):
             ordering = [ordering]
         ordering = ordering or []
@@ -12,7 +12,7 @@ def __init__(self, expression, ordering=(), **extra):
             (OrderBy(F(o[1:]), descending=True) if isinstance(o, str) and o[0] == '-' else o)
             for o in ordering
         )
-        super().__init__(expression, **extra)
+        super().__init__(*expressions, **extra)
         self.ordering = self._parse_expressions(*ordering)
 
     def resolve_expression(self, *args, **kwargs):
diff --git a/docs/releases/1.11.28.txt b/docs/releases/1.11.28.txt
new file mode 100644
index 000000000000..81ccb0ce06f8
--- /dev/null
+++ b/docs/releases/1.11.28.txt
@@ -0,0 +1,13 @@
+============================
+Django 1.11.28 release notes
+============================
+
+*February 3, 2020*
+
+Django 1.11.28 fixes a security issue in 1.11.27.
+
+CVE-2020-7471: Potential SQL injection via ``StringAgg(delimiter)``
+===================================================================
+
+:class:`~django.contrib.postgres.aggregates.StringAgg` aggregation function was
+subject to SQL injection, using a suitably crafted ``delimiter``.
diff --git a/docs/releases/2.2.10.txt b/docs/releases/2.2.10.txt
new file mode 100644
index 000000000000..f82774dea096
--- /dev/null
+++ b/docs/releases/2.2.10.txt
@@ -0,0 +1,13 @@
+===========================
+Django 2.2.10 release notes
+===========================
+
+*February 3, 2020*
+
+Django 2.2.10 fixes a security issue in 2.2.9.
+
+CVE-2020-7471: Potential SQL injection via ``StringAgg(delimiter)``
+===================================================================
+
+:class:`~django.contrib.postgres.aggregates.StringAgg` aggregation function was
+subject to SQL injection, using a suitably crafted ``delimiter``.
diff --git a/docs/releases/3.0.3.txt b/docs/releases/3.0.3.txt
index ed92938e091c..2eed2654c862 100644
--- a/docs/releases/3.0.3.txt
+++ b/docs/releases/3.0.3.txt
@@ -4,7 +4,13 @@ Django 3.0.3 release notes
 
 *Expected February 3, 2020*
 
-Django 3.0.3 fixes several bugs in 3.0.2.
+Django 3.0.3 fixes a security issue and several bugs in 3.0.2.
+
+CVE-2020-7471: Potential SQL injection via ``StringAgg(delimiter)``
+===================================================================
+
+:class:`~django.contrib.postgres.aggregates.StringAgg` aggregation function was
+subject to SQL injection, using a suitably crafted ``delimiter``.
 
 Bugfixes
 ========
diff --git a/docs/releases/index.txt b/docs/releases/index.txt
index 411ca4805ce7..6a688587ef19 100644
--- a/docs/releases/index.txt
+++ b/docs/releases/index.txt
@@ -42,6 +42,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   2.2.10
    2.2.9
    2.2.8
    2.2.7
@@ -100,6 +101,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   1.11.28
    1.11.27
    1.11.26
    1.11.25
diff --git a/tests/postgres_tests/test_aggregates.py b/tests/postgres_tests/test_aggregates.py
index af84f12e916c..a1dbe4441c72 100644
--- a/tests/postgres_tests/test_aggregates.py
+++ b/tests/postgres_tests/test_aggregates.py
@@ -169,6 +169,10 @@ def test_string_agg_requires_delimiter(self):
         with self.assertRaises(TypeError):
             AggregateTestModel.objects.aggregate(stringagg=StringAgg('char_field'))
 
+    def test_string_agg_delimiter_escaping(self):
+        values = AggregateTestModel.objects.aggregate(stringagg=StringAgg('char_field', delimiter="'"))
+        self.assertEqual(values, {'stringagg': "Foo1'Foo2'Foo4'Foo3"})
+
     def test_string_agg_charfield(self):
         values = AggregateTestModel.objects.aggregate(stringagg=StringAgg('char_field', delimiter=';'))
         self.assertEqual(values, {'stringagg': 'Foo1;Foo2;Foo4;Foo3'})