Bitcoin has finally shaken off its summer slump.

The price of a single coin BTCUSD, -0.53% has climbed above $630 for the first time since August, when reports that hackers had stolen 120,000 bitcoins, then worth more than $65 million, from one of the world’s largest bitcoin exchanges. The theft sent the price of the popular cryptocurrency spiraling lower. At its lowest point, bitcoin had lost $100 in value, though it quickly reversed much of this drop.

Read: Bitcoin price plummets after exchange loses $65 million to hackers

The hack at Hong Kong-based Bitfinex, which remains one of the largest cryptocurrency exchanges, followed another high-profile incident in June, when a hacker stole more than 3.5 million ether tokens—worth about $50 million at the time—from an entity known as the DAO. To recover the stolen coins, Ethereum’s developers engineered a controversial software update that recovered the stolen coins by essentially unwinding part of the Ethereum blockchain. Initially created as a vehicle to help crowdfund promising startups building on the Ethereum blockchain, the DAO was dissolved after the hack.

Read:Digital currency Ethereum nose-dives after $50 million hack

Bitfinex issued a newly created coin called the BFX token as a sort of a placeholder for customers who lost coins during the hack. On Thursday, the exchange announced that it would allow customers to exchange their BFX tokens for a stake in the company, with each coin valued at $1.

Security remains a concern for many investors, as exchanges have proven consistently that they are vulnerable to hackers.

Of course the most prominent example of big security issues in digital currencies occurred in February 2014, when Mt. Gox, once the dominant bitcoin exchange, collapsed after hackers stole millions of customer bitcoins. The news effectively ended the bitcoin speculative bubble of 2013, as the price of a single coin slumped to less than $200, after peaking near $1,200 in November 2013.