Bradley Bennett created GUACAMOLE-2282:
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Summary: Firefox: text copied outside the browser is not pasted
into Guacamole remote sessions
Key: GUACAMOLE-2282
URL: https://issues.apache.org/jira/browse/GUACAMOLE-2282
Project: Guacamole
Issue Type: Bug
Components: guacamole-client
Affects Versions: 1.6.0, 1.6.1 [staging]
Environment: Firefox browser, all remote protocols.
Reporter: Bradley Bennett
Attachments: image-2026-05-27-00-06-52-784.png
When copying text from another application and switching back to a Guacamole
session in Firefox, the clipboard data is often not synced into Guacamole’s
internal clipboard. As a result, pasting into the remote SSH/RDP session uses
stale or empty clipboard contents. The same workflow works correctly in Chrome.
Guacamole currently syncs the system clipboard using
*navigator.clipboard.readText()* from load, focus, copy, and cut event
handlers. Firefox blocks these clipboard reads unless they occur during a real
user gesture (click/key interaction), so the calls fail with errors like:
{code:java}
NotAllowedError: Clipboard read request was blocked due to lack of user
activation.
{code}
or:
{code:java}
NotAllowedError: Clipboard read operation is not allowed.
{code}
The existing fallback using *document.execCommand('paste')* also fails in
Firefox outside a real paste event, so the clipboard sync paths fail.
This behavior occurs even with a secure (https) connection, and cannot be
disabled in settings.
Firefox may sometimes display a temporary “{*}Paste{*}”
!image-2026-05-27-00-06-52-784.png! permission prompt when a clipboard read
happens during certain interactions. Allowing the prompt lets that specific
clipboard read succeed, but the permission is not persistent and the prompt
does not reliably appear when simply returning focus to the tab after copying
externally.
The Guacamole clipboard/paste menu itself works correctly in Firefox because it
uses a real browser paste interaction (Ctrl+V into a textarea/menu control),
which Firefox allows. The issue is specifically with automatic clipboard
syncing after copying externally and returning to the tab.
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