Hi. This bug can be reproduced by combining Alt with other modifiers (Alt+Ctrl, Alt+Shift...) and performing the selection.
I think solving this bug as suggested by https://bugzilla.mozilla.org/show_bug.cgi?id=254707 (disable link dragging by default) could pose a security issue, see attachment for a simple attack. I know Vincent was requesting something different, that could be fixed. But... wontfix, sorry, I don't have a patch.Select any word of this sentence
