Backspace(\b) doesn't work with the gsub filter

[jvayao]

Version: 6.x
Operating System: Any
Backspace(\b) doesn't work with the gsub filter:

Config:

	mutate {
		gsub => [
			"Data","\u0000","",
			"Data","\u0001","",
			"Data","\u0002","",
			"Data","\u0003","",
			"Data","\u0004","",
			"Data","\u0005","",
			"Data","\u0006","",
			"Data","\f","",
			"Data","\a","",
			"Data","\b",""
		] 
	}
	json {
		source => "Data"
	}

Log:
[2018-03-13T14:43:55,298][WARN ][logstash.filters.json ] Error parsing json {:source=>"Data", :raw=>"{\"bid\":\"00015\",\"platform\":\"AndroidPhone\",\"brand\":\"HUAWEI\",\"device\":\"ALP-TL00\",\"os\":\"8.0.0\",\"hid\":\"23e63ec86d7a48d7NDF7N17C14000402866215033164432\",\"name\":\"com.android.haitong\",\"ver\":\"81\",\"token\":\"\",\"appkey\":\"BiiilRwAYsKdk828aRMb8ktOXfaTPWAZo1tibfkrkXQ=\",\"sdk_ver\":\"1.1.19.11\",\"timestamp\":\"1520913226940\"}\b\b\b\b\b\b\b\b", :exception=>#<LogStash::Json::ParserError: Illegal character ((CTRL-CHAR, code 8)): only regular white space (\r, \n, \t) is allowed between tokens at [Source: (byte[])"{"bid":"00015","platform":"AndroidPhone","brand":"HUAWEI","device":"ALP-TL00","os":"8.0.0","hid":"23e63ec86d7a48d7NDF7N17C14000402866215033164432","name":"com.android.haitong","ver":"81","token":"","appkey":"BiiilRwAYsKdk828aRMb8ktOXfaTPWAZo1tibfkrkXQ=","sdk_ver":"1.1.19.11","timestamp":"1520913"; line: 1, column: 306]>}