Webhook CV2 Attachments does not appear as Thread thumbnail

[tintinkung]

Description

Using discord webhook on a forum channel, creating a new thread with attached images for the first message should appear as the thread's thumbnail just like when sending embed as the initial message.

However sending ComponentV2 like Media Gallery and Section Thumbnail does not appear as the thread's thumbnail.

Only tested with thread created by discord webhook.

Steps to Reproduce

1.) Send some attachment and embed it in components v2 that supports it

Attachments:

 [ {
  "filename" : "avatar-image.png",
  "id" : 0
}, {
  "filename" : "plot-image-3.png",
  "id" : 1
}, {
  "filename" : "plot-image-1.png",
  "id" : 2
}, {
  "filename" : "plot-image-2.png",
  "id" : 3
} ]

Components Data:

 {
  "components" : [ {
    "accent_color" : 5614830,
    "components" : [ {
      "type" : 10,
      "content" : "# :house: Plot #52 (XXX, XXX)",
      "id" : 16842752
    }, {
      "components" : [ {
        "type" : 10,
        "content" : "```XXX```"
      } ],
      "id" : 33619968,
      "type" : 9,
      "accessory" : {
        "style" : 5,
        "disabled" : false,
        "label" : "Google Map",
        "type" : 2,
        "url" : " https://www.google.com/maps/place/XXX"
      }
    }, {
      "type" : 12,
      "items" : [ {
        "description" : "plot-image-3.png",
        "media" : {
          "url" : "attachment://plot-image-3.png"
        },
        "spoiler" : false
      }, {
        "description" : "plot-image-1.png",
        "media" : {
          "url" : "attachment://plot-image-1.png"
        },
        "spoiler" : false
      }, {
        "description" : "plot-image-2.png",
        "media" : {
          "url" : "attachment://plot-image-2.png"
        },
        "spoiler" : false
      } ],
      "id" : 50397184
    }, {
      "spacing" : 1,
      "id" : 67174400,
      "type" : 14,
      "divider" : true
    }, {
      "type" : 10,
      "content" : "## Plot Histories\n:small_blue_diamond: XXX archived the plot XXX",
      "id" : 83951616
    } ],
    "spoiler" : false,
    "id" : 65536,
    "type" : 17
  }, {
    "accent_color" : 5614830,
    "components" : [ {
      "components" : [ {
        "type" : 10,
        "content" : "## Claimed by XXX\nThis plot is **archived**.\nYou can still visit it or continue improving it on our master server.",
        "id" : 16908289
      } ],
      "id" : 33685505,
      "type" : 9,
      "accessory" : {
        "type" : 11,
        "description" : "XXX",
        "media" : {
          "url" : "attachment://avatar-image.png"
        }
      }
    } ],
    "spoiler" : false,
    "id" : 131073,
    "type" : 17
  } ],
  "attachments" : [ {
    "filename" : "avatar-image.png",
    "id" : 0
  }, {
    "filename" : "plot-image-3.png",
    "id" : 1
  }, {
    "filename" : "plot-image-1.png",
    "id" : 2
  }, {
    "filename" : "plot-image-2.png",
    "id" : 3
  } ],
  "thread_name" : "Plot #52",
  "flags" : 36864,
  "allowed_mentions" : {
    "parse" : [ ]
  },
  "applied_tags" : [ 1361323079808192622 ]
}

2.) Send it with webhook

Execute via /webhooks/{webhook.id}/{webhook.token} with thread_id and with_components

Expected Behavior

The thread thumbnail should pick the attached image gallery or the section field's thumbnail image
Just like when you send embed with images as the thread's first message.

Current Behavior

The thread does not display any component attached images to the thumbnail.

Screenshots/Videos

Client and System Information

N/A; API V10

[DV8FromTheWorld]

I have merged a fix for this. It should be on Canary soon, stable in a bit, and will slowly makes its way out to mobile (week or two).

Thanks for bringing this up!