%% You should probably cite rfc7636 instead of this I-D.
@techreport{ietf-oauth-spop-15,
    number =    {draft-ietf-oauth-spop-15},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-oauth-spop/15/},
    author =    {Nat Sakimura and John Bradley and Naveen Agarwal},
    title =     {{Proof Key for Code Exchange by OAuth Public Clients}},
    pagetotal = 20,
    year =      2015,
    month =     jul,
    day =       10,
    abstract =  {OAuth 2.0 public clients utilizing the Authorization Code Grant are susceptible to the authorization code interception attack. This specification describes the attack as well as a technique to mitigate against the threat through the use of Proof Key for Code Exchange (PKCE, pronounced "pixy").},
}