Deploying alias configurations for prebid server through prebid.js is dangerous, because if a bidder is being disabled, it can stop the entire monetization of prebid server. Disabled bidders will stop the entire bid requests with a 400 if the alias configuration contains a disabled bidder.

🪄 Steps to reproduce

Prebid.js s2s config

    s2sConfig: [
      // Server side only configuration
      {
        accountId: accountId,
        adapter: 'prebidServer',
        endpoint: { p1Consent: 'https://prebid-server/openrtb2/auction' },
        syncEndpoint: { p1Consent: 'https://prebid-server/cookie_sync' },
        bidders: [ 'bidderA', 'bidderB' ],
        extPrebid: {
          aliases: {
            'bidder_c_alias': 'bidder_c' // note that this bidder isn't even in the bidders array
          }
        }
      }
    ],

and send a request to a prebid server where BidderC is not enabled.

This will cause a 400 with

Invalid request format: request.ext.prebid.aliases.bidder_c_alias refers to disabled bidder: bidder_c

💡 Proposal

We turn the 400 into an error metric. Related to #3209

Related

If the bidder being alias is unknown also a 400 is being returned:

Invalid request format: request.ext.prebid.aliases.bidder_c_alias refers to unknown bidder: bidder_c

which I guess is okaish, but a metric would also be better.