Just updated to

"@pulumi/pulumi": "0.17.7",
        "@pulumi/aws": "0.18.1",
        "@pulumi/awsx": "0.18.1"

and I am still getting this error message:

error: Plan apply failed: [WARN] A duplicate Security Group rule was found on (sg-002c2846717345a56). This may be
    a side effect of a now-fixed Terraform issue causing two security groups with
    identical attributes but different source_security_group_ids to overwrite each
    other in the state. See <https://github.com/hashicorp/terraform/pull/2376> for more
    information and instructions for recovery. Error message: the specified rule "peer: 0.0.0.0/0, TCP, from port: 8880, to port: 8880, ALLOW" already exists

The only fix is to go into the AWS console and remove that rule.

I think I did a

pulumi refresh

which fixed it

Do you have a repro of what triggered this initially? Did you get this directly via

new awsx.ec2.Vpc()

without any non-default options?