#373: `SameSite=Lax` by default.

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Opened May 8, 2019

Guten TAG,

I'm requesting a TAG review of:

Further details (optional):

TL;DR: We're proposing treating cookies as SameSite=Lax by defaul. Developers would be able to opt-into the status quo by explicitly asserting SameSite=None, but to do so, they'll also need to ensure that their cookies won't be delivered over non-secure transport by asserting the Secure attribute. The specification (paginated) spells out the proposal in a bit more detail.

  • Relevant time constraints or deadlines: We'd like to begin experimenting with this behavior in the relatively near future, but we're not planning on shipping it tomorrow.
  • I am more or less familiar with the Self-Review Questionnare on Security and Privacy. My assessment is that this is a privacy-positive change, as it entails a strict reduction in cookies going over the wire in plaintext, and that it will be a pretty substantial mitigation against CSRF, etc.
  • I have reviewed the TAG's API Design Principles

We'd prefer the TAG provide feedback as (please select one):

  • open issues in our GitHub repo for each point of feedback
  • open a single issue in our GitHub repo for the entire review
  • leave review feedback as a comment in this issue and @-notify [github usernames]

Thanks!

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