[L-02] Code Injection Via Token Name

Description:
Some malicious tokens have been observed to include malicious javascript in their name attribute, allowing attackers to extract private keys from users who choose to interact with these tokens via vulnerable frontends.
This has been used to exploit etherdelta users in the wild reference.

Impact:
Since there is no checks on erc20 name and symbol of the token being imported there is possibility of script injection via token name.

Recommended Mitigation:
As also recommended by the previous audit, it's absolutely necessary to sanitize the user's input on the safeAssetSymbol function as the length check is not enough. The asset symbol should only contain Aa-Zz and 0-9 characters while forbidding special ones, i.e. < / >.