We released updates to Team Foundation Server 2015 Update 4, Team Foundation Server 2017, and Team Foundation Server 2017 Update 3 to fix security vulnerabilities. You can read the details in Brian's blog post. We recommend customers install these updates. All of these fixes are also in Team Foundation Server 2018 Update 1, and we recommend customers on Team Foundation Server 2018 to upgrade to Update 1. Here are some key links:
Team Foundation Server 2015 Update 4.1:
Release Notes
TFS Server ISO
TFS Server web install
TFS Express ISO
TFS Express web install
Team Foundation Server 2017.0.1:
Release Notes
TFS Server ISO
TFS Server web install
TFS Express ISO
TFS Express web install
Team Foundation Server 2017 Update 3.1:
Release Notes
TFS Server ISO
TFS Server web install
TFS Express ISO
TFS Express web install