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Thunderbird 155 breaks packaged script loading via WindowListener and Services.scriptloader.loadSubScript() #385
Description
Summary
Thunderbird 155 blocks jar:/file: URLs passed to
Services.scriptloader.loadSubScript(), breaking legacy add-ons that use the
WindowListener Experiment to inject chrome-window scripts.
Upstream reference: Mozilla Bug 2061809.
Impact
quickFilters cannot load WindowListener-managed scripts from its packaged XPI,
including scripts registered with:
registerDefaultPrefs()registerWindow()- startup script loading
- shutdown script loading
This also affects direct calls to Services.scriptloader.loadSubScript() when the script URL resolves to a packaged jar:/file: URI - including all chrome:// scripts. WindowListener is one widely used abstraction that exposes the breakage.
The same patterns are used by QuickFolders, SmartTemplates, and FiltaQuilla.
Proposed short-term fix
Keep the existing WindowListener API and all add-on registration calls unchanged.
Only update the WindowListener Experiment implementation to load scripts via:
Services.scriptloader.loadSubScriptWithOptions(url, {
target,
charset: "UTF-8",
allowUnsafeURL: true,
});
Activity
RealRaven2000 commentedon Aug 12, 2026
Here is the complete list of exceptions in Thunderbird Daily 155.0a1 (2026-08-12) (64-bit) on startup:
and here is a list of error when opening message filters dialog:
Trying to load untrusted URI.: jar:file:///I:/Thunderbird_Profiles/in5mky4p.Tb91-fix/extensions/quickFilters@axelg.com.xpi!/chrome/content/scripts/qFi-filterlist.js implementation.js:729and opening the filter editor:
RealRaven2000 commentedon Aug 12, 2026
Fix: using
loadSubScriptWithOptions()to force unsafe URL. This is to fix the Add-on not loading anymore in Thunderbird 155 Daily because untrusted URI issues caused by Bug 1974213 "Don't allow file: and jar: schemes inServices.scriptloader.loadSubScript"Merge pull request #386 from RealRaven2000/windowlistener-loadsubscri…
#385
RealRaven2000 commentedon Sep 1, 2026
Implemented in 6.13.3 - Published 31/08/2026