Ampersand (&) symbol appears corrupt on some Firefox configurations

[Osspial]

On my Firefox build, running version 51.0.1 stable, the & symbol appears corrupt as shown above. When Firefox is started in safe mode, the symbols just don't render instead of appearing corrupt (as shown below) - however, if all add-ons are manually disabled and Firefox is run outside of safe mode, the symbol appears like it does above.

List of add-ons:

• LastPass
• Min Vid (Firefox Test Pilot)
• Octotree
• Private Tab
• Reddit Enhancement Suite
• snoozetabs (Firefox Test Pilot)
• Tab Mix Plus
• Tree Style Tab
• uBlock Origin

[shepmaster]

This is a semi-known issue. The short version is that your local version of the fonts are screwed up in some way (rust-lang/rust#16372; rust-lang/rust#34120).

It should also be possible to avoid this problem completely by always forcing the font to come from the web, ignoring any broken local versions (rust-lang/rust#38164). That forces more network traffic for everyone.