Secure your app: threat modeling and anti-patterns

func handleIncomingFile(_ incomingResourceURL: URL, with name: String, from fromID: String) {
    guard
         case let safeFileName = name.lastPathComponent, 
         safeFileName.count > 0,
         safeFileName != "..", safeFileName != "." else { return }

    let destinationFileURL = URL(fileURLWithPath: NSTemporaryDirectory())
                                 .appendingPathComponent(safeFileName)

    // Copy the file into a temporary directory
    try! FileManager.default.copyItem(at: incomingResourceURL, to: destinationFileURL)

}

func handleSessionInviteAccepted(with message: RemoteMessage, from fromID: String) {
    guard session = sessionsByIdentifier[message.sessionIdentifier],
          session.state == .inviting,
          session.invitedFromIdentifiers.contains(fromID) else { return }

    session.state = .connected
    session.setupSocket(to: fromID) { socket in
        cameraController.send(to: socket)
    }
}

NSSet *classesWhichConformToProtocol(Protocol *protocol) {
    NSMutableSet *conformingClasses = [NSMutableSet set];
    
    unsigned int classesCount = 0;
    Class *classes = objc_copyClassList(&classesCount);
    if (classes != NULL) {
        for (unsigned int i = 0; i < classesCount; i++) {
            if (class_conformsToProtocol(classes[i], protocol)) {
                [conformingClasses addObject: classes[i]];
            }
        }
        free(classes);
    }
    return conformingClasses;
}

@implementation
- (BOOL)unpackTeaClubRecord:(CKRecord *)record {
    ...
    NSData *data = [record objectForKey:@"uuid"];
    if (data == nil ||
        ![data isKindOfClass:[NSData class]] ||
        data.length != sizeof(_uuid)) {
        return NO;
    }
    memcpy(&_uuid, data.bytes, data.length);
    ...

@implementation
- (BOOL)unpackTeaClubRecord:(CKRecord *)record {
    ...
    NSData *name = [record objectForKey:@"name"];
    int32_t count = [[record objectForKey:@"nameCount"] unsignedIntegerValue];
    int32_t byteCount = 0;
    if (name == nil ||
        ![name isKindOfClass:[NSData class]] ||
        os_mul_overflow(count, sizeof(unichar), &byteCount) ||
        name.length != byteCount) {
        return NO;
    }
    _name = [[NSString alloc] initWithCharacters:name.bytes 
                                          length:count];
    ...