In Progress MergedEvent crashes on PHP 8 when agent name contains URL-encoded characters

Environment:

• osTicket-1.18.3-Awesome-104
• PHP 8.3.6

When viewing a ticket containing merged child tickets, osTicket throws a fatal PHP error:

PHP Fatal error: Uncaught ValueError: Unknown format specifier "C"

The error originates from:

include/class.thread.php

class MergedEvent extends ThreadEvent {
function getDescription($mode=self::MODE_STAFF) {
return sprintf(
$this->template(
__('{somebody} merged this ticket with %s{data.id}%s{data.ticket}%s {timestamp}'),
$mode
),
'', ''
);
}
}

Stack trace points directly to the sprintf() call.

Root Cause:
The {somebody} placeholder is expanded before sprintf() is executed.

In our installation the merged event was created by an agent named:

Casper F. Sørensen

The generated HTML contains an avatar URL with URL-encoded characters:

name=Casper+F.+S%C3%B8rensen

After placeholder substitution, sprintf() receives a string containing:

%C3%B8

PHP 8 interprets "%C" as a format specifier and throws:

ValueError: Unknown format specifier "C"

This causes the entire ticket thread rendering to fail.

Example Debug Output:
Template result:

<img class="avatar" ... name=Casper+F.+S%C3%B8rensen" />Casper F. Sørensen
merged this ticket with 344
Ticket #S416

Expected Behavior:
Merged ticket events should render correctly regardless of agent names containing non-ASCII characters such as:

ø
æ
å
ü
é
etc.

Actual Behavior:
Ticket thread rendering fails with a fatal PHP error.

Suggested Fix:
Avoid using sprintf() after placeholder expansion.

One possible approach:

Build the link placeholders before template rendering.
Use str_replace() instead of sprintf().
Escape literal percent signs before passing strings to sprintf().

For example:

return str_replace(
array('LINK_START', 'LINK_MID', 'LINK_END'),
array('', ''),
$this->template(__($raw), $mode)
);

Impact:
Any merged ticket can become unreadable when the merge event was performed by an agent whose display name results in URL-encoded percent sequences being present in the rendered HTML.

This appears to be a PHP 8 compatibility issue rather than a localization or theme issue.