[wp-trac] [WordPress Trac] #40917: Some HTTP headers are duplicated on admin-ajax.php responses

[WordPress Trac]

#40917: Some HTTP headers are duplicated on admin-ajax.php responses
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 Reporter:  EatonZ          |       Owner:
     Type:  defect (bug)    |      Status:  closed
 Priority:  normal          |   Milestone:
Component:  Administration  |     Version:  4.7.5
 Severity:  normal          |  Resolution:  invalid
 Keywords:                  |     Focuses:
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Changes (by dd32):

 * status:  new => closed
 * resolution:   => invalid
 * milestone:  Awaiting Review =>


Comment:

 Hi @EatonZ,

 Unfortunately it looks like this is probably a "bug" in IIS - probably an
 expected scenario.

 It looks like IIS simply appends the specified headers to whatever PHP
 outputs, which means WordPress is unable to detect that the headers are
 going to apply - We could parse the web.config file on each pageload, but
 that would be inefficient and likely not very precise.

 The duplicated headers are not actually a problem for most clients, and
 given they're the same values shouldn't cause any issue.

 I'm going to close this as `invalid` due to that, but if you're aware of a
 method that WordPress could avoid this scenario we could re-open it.

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Ticket URL: <https://core.trac.wordpress.org/ticket/40917#comment:1>
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