I have debugged this issue a bit and found, that the runners/bookmarks/faviconfromblob.cpp file in plasma-workspace tries to access the table moz_favicons in the sqlite database (line 80) which doesn't exist though. Checking the firefox source code, I found mentions that since Firefox 37 the table was not used anymore and since Firefox 41 the table was dropped. I have no idea why this wasn't an issue before but it might be because of a newer Qt version that broke something? $ sqlite3 .cache/krunnerbookmarkrunnerfirefoxdbfile.sqlite SQLite version 3.22.0 2018-01-22 18:45:57 Enter ".help" for usage hints. sqlite> .tables moz_anno_attributes moz_historyvisits moz_keywords moz_annos moz_hosts moz_places moz_bookmarks moz_inputhistory moz_bookmarks_deleted moz_items_annos gdb backtrace (without Qt debug symbols): (gdb) bt #0 0x00007ffff41cba60 in QVariant::QVariant(QVariant const&) () at /usr/lib/libQt5Core.so.5 #1 0x00007fffb7d682cc in () at /usr/lib/qt/plugins/sqldrivers/libqsqlite.so #2 0x00007fffb7d65ae6 in () at /usr/lib/qt/plugins/sqldrivers/libqsqlite.so #3 0x00007fffeef07938 in QSqlQuery::exec() () at /usr/lib/libQt5Sql.so.5 #4 0x00007fffb7f7c761 in FetchSqlite::query(QString const&, QMap<QString, QVariant>) (this=this@entry=0x555557af0420, sql=..., bindObjects=...) at /tmp/plasma-workspace/trunk/src/plasma-workspace-5.12.1/runners/bookmarks/fetchsqlite.cpp:80 #5 0x00007fffb7f7cf0a in FetchSqlite::query(BuildQuery*, QMap<QString, QVariant>) (this=this@entry=0x555557af0420, buildQuery=0x555557a6a0a0, bindObjects=...) at /tmp/plasma-workspace/trunk/src/plasma-workspace-5.12.1/runners/bookmarks/fetchsqlite.cpp:67 #6 0x00007fffb7f77972 in FaviconFromBlob::iconFor(QString const&) (this=0x555557a776a0, url=...) at /tmp/plasma-workspace/trunk/src/plasma-workspace-5.12.1/runners/bookmarks/faviconfromblob.cpp:132 #7 0x00007fffb7f751b5 in BookmarkMatch::asQueryMatch(Plasma::AbstractRunner*) (this=this@entry=0x7fff957f9c70, runner=runner@entry=0x555557a6a330) at /tmp/plasma-workspace/trunk/src/plasma-workspace-5.12.1/runners/bookmarks/bookmarkmatch.cpp:63 #8 0x00007fffb7f80064 in BookmarksRunner::match(Plasma::RunnerContext&) (this=0x555557a6a330, context=...) at /tmp/plasma-workspace/trunk/src/plasma-workspace-5.12.1/runners/bookmarks/bookmarksrunner.cpp:85 #9 0x00007fffd10887f0 in Plasma::AbstractRunner::performMatch(Plasma::RunnerContext&) (this=0x555557a6a330, localContext=...) at /tmp/krunner/trunk/src/krunner-5.43.0/src/abstractrunner.cpp:130 #10 0x00007fffd0e67618 in ThreadWeaver::Executor::run(QSharedPointer<ThreadWeaver::JobInterface> const&, ThreadWeaver::Thread*) () at /usr/lib/libKF5ThreadWeaver.so.5 #11 0x00007fffd0e66610 in ThreadWeaver::Job::execute(QSharedPointer<ThreadWeaver::JobInterface> const&, ThreadWeaver::Thread*) () at /usr/lib/libKF5ThreadWeaver.so.5 #12 0x00007fffd0e65d45 in ThreadWeaver::Thread::run() () at /usr/lib/libKF5ThreadWeaver.so.5 #13 0x00007ffff3f98b4d in () at /usr/lib/libQt5Core.so.5 #14 0x00007ffff17f208c in start_thread () at /usr/lib/libpthread.so.0 #15 0x00007ffff38a0e7f in clone () at /usr/lib/libc.so.6 If the backtrace from Qt is needed, I can recompile Qt with debug symbols.
*** This bug has been marked as a duplicate of bug 363136 ***