Bug 1773207 fixed a regression where the com.apple.quarantine extended attribute was not being removed from downloaded GMP plugin dylibs.
As a result of the regression some profiles will have a downloaded GMP plugin dylib that will fail to load even with the fix for 1773207.
This bug is filed to cover adding a fix to clear the quarantine attribute on plugins already downloaded that are affected by 1773207. We could add code to clear the attribute before using the plugin. We might also be able to use the method we used in bug 1587537 where we shipped a new plugin version causing a re-download of the plugin.
Clearing of the quarantine attribute was added back in bug 1566523 to support macOS 10.15 which released with stronger rules about loading downloaded dylibs.