Closed Bug 2061355 Opened 3 days ago Closed 2 days ago

Windows 10: Cannot drag attachments to Windows Explorer/Desktop after upgrade to Thunderbird 153.0.2 ESR

Categories

(Thunderbird :: Folder and Message Lists, defect)

Product:
Thunderbird
Component:
Folder and Message Lists
Version:
Thunderbird 153
Type:
defect

Tracking

(Not tracked)

Status:
RESOLVED DUPLICATE of bug 2060748

People

(Reporter: todd, Unassigned)

References

(Blocks 1 open bug)

Details

Attachments

(1 file)

image.png
1.12 MB, image/png
Details

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:153.0) Gecko/20100101 Firefox/153.0

Steps to reproduce:

The following tests were completed:

  • Thunderbird is not running as Administrator.
  • Windows Explorer is not elevated.
  • Restarted Windows Explorer.
  • Disabled Windows Defender Controlled Folder Access.
  • Problem persists.
  • Dragging the same attachment into Microsoft Word works.
  • Dragging the same attachment into Notepad works.
  • Dragging PDF attachments fails.
  • Dragging PNG attachments fails.
  • Created a new compose message, attached a local PDF from disk, and attempted to drag that attachment to the Desktop.
  • The locally attached PDF is also rejected by Explorer with the "Not Allowed" cursor.

Actual results:

Title

Windows 10: Cannot drag attachments to Windows Explorer/Desktop after upgrading to Thunderbird 153.0.2 ESR (Explorer displays "Not Allowed" cursor)

Product: Thunderbird

Version: 153.0.2 ESR (64-bit)

Operating System: Windows 10 (64-bit)

Build ID: 20260804042004

Summary

After upgrading to Thunderbird 153.0.2 ESR, dragging attachments from Thunderbird to Windows Explorer or the Windows Desktop no longer works.

The mouse cursor changes to the Windows "Not Allowed" cursor (circle with slash), and the drop is rejected.

Drag-and-drop to other applications such as Microsoft Word and Notepad continues to work normally.

The issue began immediately after updating to Thunderbird 153.0.2 ESR.

Steps to Reproduce

  1. Open Thunderbird 153.0.2 ESR on Windows 10.

  2. Open an email containing an attachment (tested with PDF and PNG files).

  3. Drag the attachment to:

    • Windows Explorer
    • Windows Desktop

Actual Results

Explorer/Desktop displays the "Not Allowed" cursor and rejects the drop.

No file is created.

Expected Results

The attachment should be copied to the selected Explorer folder or Desktop.

Additional Testing Performed

The following tests were completed:

  • Thunderbird is not running as Administrator.
  • Windows Explorer is not elevated.
  • Restarted Windows Explorer.
  • Disabled Windows Defender Controlled Folder Access.
  • Problem persists.
  • Dragging the same attachment into Microsoft Word works.
  • Dragging the same attachment into Notepad works.
  • Dragging PDF attachments fails.
  • Dragging PNG attachments fails.
  • Created a new compose message, attached a local PDF from disk, and attempted to drag that attachment to the Desktop.
  • The locally attached PDF is also rejected by Explorer with the "Not Allowed" cursor.

This suggests the issue is independent of:

  • IMAP/POP storage
  • MIME decoding
  • Downloaded message attachments

and appears related to Thunderbird's Windows drag-and-drop implementation when interacting with Explorer.

Environment

  • Windows 10
  • Thunderbird 153.0.2 ESR (64-bit)
  • Build ID: 20260804042004

Troubleshooting Information:

  • Multiprocess Windows: 0/0
  • Accessibility: false
  • Application Binary:
    C:\Program Files\Mozilla Thunderbird\thunderbird.exe

Regression

The problem started immediately after updating to Thunderbird 153.0.2 ESR.

Drag-and-drop to Explorer/Desktop worked correctly prior to the update.

Drag-and-drop continues to function when the destination application is Microsoft Word or Notepad, suggesting the regression is specific to Windows Explorer/Desktop integration.

Expected results:

drag-and-drop into explorer/desktop should work normally

Additional diagnostics:

Windows 10 (64-bit)
Thunderbird 153.0.2 ESR (64-bit)
Build ID: 20260804042004
Issue began immediately after upgrading to 153.0.2 ESR.
Thunderbird is not running elevated.
Windows Explorer is not elevated.
Restarting Windows Explorer did not resolve the issue.
Disabling Windows Defender Controlled Folder Access did not resolve the issue.
No third-party antivirus or endpoint security software is installed (Microsoft Defender only).
Dragging attachments (tested with PDF and PNG) to Windows Explorer or the Desktop shows the "Not Allowed" cursor.
Dragging email messages (.eml) to Windows Explorer or the Desktop also shows the "Not Allowed" cursor.
Drag-and-drop from Thunderbird into Microsoft Word and Notepad works normally.
The issue also occurs when dragging a locally attached PDF from a compose window to the Desktop, indicating it is not limited to received message attachments.

Vlad/Ramona, can you recreate and run mozregression?

Flags: needinfo?(vlucaci)
Flags: needinfo?(ramona)
Blocks: tb153found

Variation?

Attached image image.png —

Hello!

I have managed to reproduce this issue on Windows and also able to pull a regression range. It seems that the regression was introduced somewhere between 2026-07-29 and 2026-07-30.

Adding a picture of how it has manifested for me (as the attachment provided by Ed in comment 3).

Below you can find the regression range:

https://hg-edge.mozilla.org/comm-central/pushloghtml?fromchange=d261a283329ef8cb5b95b2835f2930616f533add&tochange=744a4bec8a1b9dd60ffaabd8a69d88696ac9ff23
hg-edge.mozilla.orgcomm-central pushlog feedRendered pushlog feed for comm-central[11:28 AM]2026-08-07T11:27:31.173000: DEBUG : Found commit message:
Bug 2058239 - Disable custom scheme OAuth2 flow on ESR. r=thunderbird-reviewers,babolivier

Differential Revision: https://phabricator.services.mozilla.com/D314434

2026-08-07T11:27:31.175000: DEBUG : Did not find a branch, checking all integration branches
2026-08-07T11:27:31.176000: INFO : The bisection is done.
2026-08-07T11:27:31.180000: INFO : Stopped

Flags: needinfo?(vlucaci)
Flags: needinfo?(ramona)

Todd, you don't see "unspecified error" as documented in bug 2060748?

Flags: needinfo?(todd)

I can confirm the same drag-and-drop issue on two Windows computers running Thunderbird 153.0.2 ESR. Holding Ctrl during drag-and-drop works as a workaround.
However, after the same update, third-party software using Thunderbird to create or send emails also fails.

(In reply to Wayne Mery (:wsmwk) from comment #5)

Todd, you don't see "unspecified error" as documented in bug 2060748?

I am getting the 'unspecified error' message, as well. As of this morning (8/7).

Flags: needinfo?(todd)
Status: UNCONFIRMED → RESOLVED
Closed: 2 days ago
Duplicate of bug: 2060748
Resolution: --- → DUPLICATE
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