https://macmule.com/2015/09/25/updating-safari-extensions/

UpdateSafariExtension.bash

#!/bin/bash
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#
# License: https://macmule.com/license/
#
####################################################################################################
#
####################################################################################################
#
# DEFINE VARIABLES & READ IN PARAMETERS
#
####################################################################################################

# HARDCODED VALUE FOR "PATHTOEXTENSION" IS SET HERE
extensionRegex=""
pathToExtension=""

# CHECK TO SEE IF A VALUE WAS PASSED IN PARAMETER 4 AND, IF SO, ASSIGN TO "extensionRegex"
if [ "$4" != "" ] && [ "$extensionRegex" == "" ];
then
    extensionRegex=$4
fi

# Error if variable appName is empty
if [ "$extensionRegex" == "" ];
then
    echo "Error:  No value was specified for the extensionRegex variable..."
    exit 1
fi

# CHECK TO SEE IF A VALUE WAS PASSED IN PARAMETER 5 AND, IF SO, ASSIGN TO "pathToExtension"
if [ "$5" != "" ] && [ "$pathToExtension" == "" ];
then
    pathToExtension=$5
fi

# Error if variable appName is empty
if [ "$pathToExtension" == "" ];
then
    echo "Error:  No value was specified for the pathToExtension variable..."
    exit 1
fi

####################################################################################################

## Increments for echo at end
extensionCount=0

## Echo what we're doing
echo "Replacing extensions with a name matching: $extensionRegex  with extension located at $pathToExtension..."

## Check for home folders under /Users/
for userHome in /Users/*;
do
    ## If the below folder exists
    if [ -d "${userHome}/Library/Safari/Extensions" ];
    then
        ## Check for the Extension, using the regex as specified at $4 then replace with the Extension at path $5
            find "${userHome}/Library/Safari/Extensions" -type f -regex '.*'"$extensionRegex"'.*' -exec cp -v "${pathToExtension}" "{}" \;
        ## Increments
        extensionCount=$((extensionCount+1))
    fi
done

## If we've not incremented this variable, then no extensions found
if [ $extensionCount == 0 ];
then
    echo "No Extensions found to update in any Home folders..."
## Echo number of home folders we've updated extensions in
else
    echo "Extensions updated in $extensionCount Home folders..."
fi