diff --git a/CHANGES.md b/CHANGES.md
index 91be1e113a..67e45d61d6 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,9 @@
+## Changes in 0.20.14 (2021-12-09)
+
+🐛 Bugfixes
+
+- Sending blank m.room.encryption on iOS will disable encryption ([Security advisory](https://github.com/matrix-org/matrix-ios-sdk/security/advisories/GHSA-fxvm-7vhj-wj98))
+
 ## Changes in 0.20.13 (2021-12-06)
 
 Others
diff --git a/MatrixSDK.podspec b/MatrixSDK.podspec
index 3795ee19ba..a5779732ae 100644
--- a/MatrixSDK.podspec
+++ b/MatrixSDK.podspec
@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name         = "MatrixSDK"
-  s.version      = "0.20.13"
+  s.version      = "0.20.14"
   s.summary      = "The iOS SDK to build apps compatible with Matrix (https://www.matrix.org)"
 
   s.description  = <<-DESC
diff --git a/MatrixSDK/Crypto/MXCrypto.m b/MatrixSDK/Crypto/MXCrypto.m
index 9b70a251b1..6191ec9065 100644
--- a/MatrixSDK/Crypto/MXCrypto.m
+++ b/MatrixSDK/Crypto/MXCrypto.m
@@ -2039,19 +2039,21 @@ - (MXDeviceInfo *)eventSenderDeviceOfEvent:(MXEvent *)event
 
 - (BOOL)setEncryptionInRoom:(NSString*)roomId withMembers:(NSArray<NSString*>*)members algorithm:(NSString*)algorithm inhibitDeviceQuery:(BOOL)inhibitDeviceQuery
 {
-    // If we already have encryption in this room, we should ignore this event
-    // (for now at least. Maybe we should alert the user somehow?)
     NSString *existingAlgorithm = [_store algorithmForRoom:roomId];
     if (existingAlgorithm && ![existingAlgorithm isEqualToString:algorithm])
     {
-        MXLogDebug(@"[MXCrypto] setEncryptionInRoom: Ignoring m.room.encryption event which requests a change of config in %@", roomId);
-        return NO;
+        MXLogWarning(@"[MXCrypto] setEncryptionInRoom: New m.room.encryption event in %@ with an algorithm change from %@ to %@", roomId, existingAlgorithm, algorithm);
+        
+        // Reset the current encryption in this room.
+        // If the new algo is supported, it will be used
+        // Else, encryption and sending will be no more possible in this room
+        [roomEncryptors removeObjectForKey:roomId];
     }
 
     Class encryptionClass = [[MXCryptoAlgorithms sharedAlgorithms] encryptorClassForAlgorithm:algorithm];
     if (!encryptionClass)
     {
-        MXLogDebug(@"[MXCrypto] setEncryptionInRoom: Unable to encrypt with %@", algorithm);
+        MXLogError(@"[MXCrypto] setEncryptionInRoom: Unable to encrypt with %@", algorithm);
         return NO;
     }
 
diff --git a/MatrixSDK/Data/MXRoomState.m b/MatrixSDK/Data/MXRoomState.m
index 26cb38e01c..b42525c231 100644
--- a/MatrixSDK/Data/MXRoomState.m
+++ b/MatrixSDK/Data/MXRoomState.m
@@ -358,7 +358,7 @@ - (MXRoomGuestAccess)guestAccess
 
 - (BOOL)isEncrypted
 {
-    return (0 != self.encryptionAlgorithm.length);
+    return stateEvents[kMXEventTypeStringRoomEncryption] != nil;
 }
 
 - (NSArray<NSString *> *)pinnedEvents
diff --git a/MatrixSDK/Data/Store/MXFileStore/MXFileStore.m b/MatrixSDK/Data/Store/MXFileStore/MXFileStore.m
index 2d36c4a4ca..beffb09178 100644
--- a/MatrixSDK/Data/Store/MXFileStore/MXFileStore.m
+++ b/MatrixSDK/Data/Store/MXFileStore/MXFileStore.m
@@ -28,7 +28,7 @@
 #import "MXTools.h"
 #import "MatrixSDKSwiftHeader.h"
 
-static NSUInteger const kMXFileVersion = 76;
+static NSUInteger const kMXFileVersion = 77;
 
 static NSString *const kMXFileStoreFolder = @"MXFileStore";
 static NSString *const kMXFileStoreMedaDataFile = @"MXFileStore";
diff --git a/MatrixSDK/MatrixSDKVersion.m b/MatrixSDK/MatrixSDKVersion.m
index 343e512f6e..c1b38a41f5 100644
--- a/MatrixSDK/MatrixSDKVersion.m
+++ b/MatrixSDK/MatrixSDKVersion.m
@@ -16,4 +16,4 @@
 
 #import <Foundation/Foundation.h>
 
-NSString *const MatrixSDKVersion = @"0.20.13";
+NSString *const MatrixSDKVersion = @"0.20.14";
diff --git a/MatrixSDKTests/MXCryptoTests.m b/MatrixSDKTests/MXCryptoTests.m
index 2e2c5c83f6..ad162aacbb 100644
--- a/MatrixSDKTests/MXCryptoTests.m
+++ b/MatrixSDKTests/MXCryptoTests.m
@@ -3056,6 +3056,79 @@ - (void)testFallbackKeySignatures
     }];
 }
 
+// Test encryption algorithm change with a blank m.room.encryption event
+// - Alice and bob in a megolm encrypted room
+// - Send a blank m.room.encryption event
+// -> The room should be still marked as encrypted
+// -> It must be impossible to send a messages (because the algorithm is not supported)
+// - Fix e2e algorithm in the room
+// -> The room should be still marked as encrypted with the right algorithm
+// -> It must be possible to send message again
+// -> The message must be e2e encrypted
+- (void)testEncryptionAlgorithmChange
+{
+    // - Alice and bob in a megolm encrypted room
+    [matrixSDKTestsE2EData doE2ETestWithAliceAndBobInARoom:self cryptedBob:YES warnOnUnknowDevices:NO readyToTest:^(MXSession *aliceSession, MXSession *bobSession, NSString *roomId, XCTestExpectation *expectation) {
+        
+        MXRoom *roomFromAlicePOV= [aliceSession roomWithRoomId:roomId];
+        
+        // - Send a blank m.room.encryption event
+        [roomFromAlicePOV sendStateEventOfType:kMXEventTypeStringRoomEncryption
+                                       content:@{ }
+                                      stateKey:nil
+                                       success:nil
+                                       failure:^(NSError *error) {
+            XCTFail(@"Cannot set up intial test conditions - error: %@", error);
+            [expectation fulfill];
+        }];
+        
+        __block id listener = [roomFromAlicePOV listenToEventsOfTypes:@[kMXEventTypeStringRoomEncryption] onEvent:^(MXEvent *event, MXTimelineDirection direction, MXRoomState *roomState) {
+            
+            [roomFromAlicePOV removeListener:listener];
+            
+            [roomFromAlicePOV liveTimeline:^(MXEventTimeline *liveTimeline) {
+                
+                // -> The room should be still marked as encrypted
+                XCTAssertTrue(liveTimeline.state.isEncrypted);
+                XCTAssertEqual(liveTimeline.state.encryptionAlgorithm.length, 0);   // with a nil algorithm
+                XCTAssertTrue(roomFromAlicePOV.summary.isEncrypted);
+                
+                // -> It must be impossible to send a messages (because the algorithm is not supported)
+                [roomFromAlicePOV sendTextMessage:@"An encrypted message" success:^(NSString *eventId) {
+                    XCTFail(@"It should not possible to send encrypted message anymore");
+                } failure:^(NSError *error) {
+
+                    // - Fix e2e algorithm in the room
+                    [roomFromAlicePOV enableEncryptionWithAlgorithm:kMXCryptoMegolmAlgorithm success:^{
+                        
+                        // -> The room should be still marked as encrypted with the right algorithm
+                        XCTAssertTrue(liveTimeline.state.isEncrypted);
+                        XCTAssertEqualObjects(liveTimeline.state.encryptionAlgorithm, kMXCryptoMegolmAlgorithm);
+                        XCTAssertTrue(roomFromAlicePOV.summary.isEncrypted);
+                        
+                        // -> It must be possible to send message again
+                        [roomFromAlicePOV sendTextMessage:@"An encrypted message" success:nil failure:^(NSError *error) {
+                            XCTFail(@"The request should not fail - NSError: %@", error);
+                            [expectation fulfill];
+                        }];
+                        
+                        [roomFromAlicePOV listenToEventsOfTypes:@[kMXEventTypeStringRoomMessage] onEvent:^(MXEvent *event, MXTimelineDirection direction, MXRoomState *roomState) {
+                            // -> The message must be e2e encrypted
+                            XCTAssertTrue(event.isEncrypted);
+                            XCTAssertEqualObjects(event.wireContent[@"algorithm"], kMXCryptoMegolmAlgorithm);
+                            [expectation fulfill];
+                        }];
+                        
+                    } failure:^(NSError *error) {
+                        XCTFail(@"The request should not fail - NSError: %@", error);
+                        [expectation fulfill];
+                    }];
+                }];
+            }];
+        }];
+    }];
+}
+
 @end
 
 #pragma clang diagnostic pop