We had a discussion about this topic on Twitter 
https://twitter.com/Apl3b/status/1064854507606208513

Outcome is POST requires a backend to receive the request so it’s not a viable 
solution for SPAs.

> Am 20.11.2018 um 23:29 schrieb John Bradley <[email protected]>:
> 
> Post response works OK for server based clients.  I don't think POST works 
> for single page applications.  
> 
> Basically that would be something more like postmessage between two JS apps.  
> 
> Postmessage also has security issues passing a access token and leaking.  
> 
> Perhaps someone more familiar with SPA can comment on POST.  
> 
> John B. 
> 
> 
> 
> On Tue, Nov 20, 2018, 6:40 PM George Fletcher <[email protected] wrote:
> Hi Mike,
> 
> The Form Post Response Mode keeps the access_token out of the URL, but it 
> doesn't prevent the token from traversing through the browser. So a 
> man-in-the-browser attack may be able to intercept the values. It should help 
> with leakage in logs.
> 
> Thanks,
> George
> 
> On 11/20/18 4:00 PM, Mike Jones wrote:
>> Next question – doesn’t using the Form Post Response Mode 
>> https://openid.net/specs/oauth-v2-form-post-response-mode-1_0.html mitigate 
>> the threats you’re describing below John?  If so, I believe the Security 
>> Topics draft should say this.
>> 
>>  
>> 
>> I believe we owe it to readers to present the complete picture, which is why 
>> I believe that describing profiles using ID Tokens and the Form Post 
>> Response Mode are in scope.
>> 
>>  
>> 
>>                                                        -- Mike
>> 
>>  
>> 
>> From: OAuth <[email protected]> On Behalf Of John Bradley
>> Sent: Tuesday, November 20, 2018 7:47 AM
>> To: [email protected]
>> Subject: Re: [OAUTH-WG] OAuth Security Topics -- Recommend authorization 
>> code instead of implicit
>> 
>>  
>> 
>> Yes the at_hash protects the client from accepting an injected AT. 
>> 
>> Unfortunately it doesn't do anything to protect against leakage in logs or 
>> redirects.
>> 
>> So without the AT using some sort of POP mechanism it is hard to say sending 
>> it in a redirect is a good security practice.
>> 
>> John B.
>> 
>> On 11/20/2018 4:35 AM, Torsten Lodderstedt wrote:
>> 
>> Hi Mike, 
>>  
>> I agree that OIDC hybrid flows offer additional security over the OAuth 
>> implicit grant and are used in the wild. On my slides and in the initial 
>> version of the new section, we had included the hybrid OIDC flows because of 
>> their known token injection countermeasures.
>>  
>> I nevertheless feel very uncomfortable to recommend those flows and any flow 
>> issuing access tokens in the front channel. In the course of the detailed 
>> review of the new text we realized two issues: 
>>  
>> 1) Since the access token is exposed in the URL, such flows possess a 
>> significantly higher risk to leak the access token (e.g. through browser 
>> history, open redirection and even referrer headers) than the code grant.
>> 2) There is no viable way to sender constrain access tokens issued in the 
>> front channel. Given the WG decided to recommend use of sender constraint 
>> tokens 
>> (https://tools.ietf.org/html/draft-ietf-oauth-security-topics-09#section-2...2),
>>  it seems contradictory to recommend response types not supporting such an 
>> approach. 
>>  
>> kind regards,
>> Torsten. 
>>  
>> Am 19.11.2018 um 23:13 schrieb Mike Jones 
>> <[email protected]>:
>>  
>> This description of the situation is an oversimplification..  OpenID Connect 
>> secures the implicit flow against token injection attacks by including the 
>> at_hash (access token hash) in the ID Token, enabling the client to validate 
>> that the access token was created by the issuer in the ID Token (which is 
>> also the OAuth Issuer, as described in RFC 8414).  (Note that this 
>> mitigation was described in draft-ietf-oauth-mix-up-mitigation.)
>>  
>> Given the prevalence of this known-good solution for securing the implicit 
>> flow, I would request that the draft be updated to describe this mitigation. 
>>  At the same time, I’m fine with the draft recommending the code flow over 
>> the implicit flow when this mitigation is not used.
>>  
>>                                                                 Thank you,
>>                                                                 -- Mike
>>  
>> From: OAuth <[email protected]> On Behalf Of Hannes Tschofenig
>> Sent: Monday, November 19, 2018 2:34 AM
>> To: oauth <[email protected]>
>> Subject: [OAUTH-WG] OAuth Security Topics -- Recommend authorization code 
>> instead of implicit
>>  
>> Hi all,
>>  
>> The authors of the OAuth Security Topics draft came to the conclusion that 
>> it is not possible to adequately secure the implicit flow against token 
>> injection since potential solutions like token binding or JARM are in an 
>> early stage of adoption. For this reason, and since CORS allows 
>> browser-based apps to send requests to the token endpoint, Torsten suggested 
>> to use the authorization code instead of the implicit grant in call cases in 
>> his presentation 
>> (seehttps://datatracker.ietf.org/meeting/103/materials/slides-103-oauth-sessb-draft-ietf-oauth-security-topics-01).
>>  
>> A hum in the room at IETF#103 concluded strong support for his 
>> recommendations. We would like to confirm the discussion on the list.
>>  
>> Please provide a response by December 3rd.
>>  
>> Ciao
>> Hannes & Rifaat
>>  
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