Windows: Pale Moon (with GreaseMonkey) (Pale Moon is basically Firefox that works the way it was meant to)
OSX: I haven't had a chance to test, please let me know your findings in the comments.
What is this Script?
TL;DR: The pictures provided should give you... the picture.
The "Add Links to Reverso" script aims to make Reverso more useful. At the moment, it works for English-Spanish. It adds links to definitions in the Diccionario de la Lengua Española (DLE) of the Asociación de Academias de la Lengua Española as well as to pronunciation on Forvo and definitions or context on Linguee, WordRef, the Corpus of the Real Academia Española (RAE) and other resources.
The current version works in two modes:
From Spanish (link to the word in the DLE, on Forvo and other resources)
To Spanish (DLE links to all the suggested translations)
Comments on Versions
Version 2+ relies on direct DOM manipulation, which is slower, but more advisable on dynamic pages
Version 1 relied on document.body.innerHTML.replace