Unfair market creation may occur

[hats-bug-reporter]

Github username: --
Twitter username: --
Submission hash (on-chain): 0x7d7960ddc0b24a8df45a0269be92260eba8af1f0faf794842ff470dbb1f37d7b
Severity: medium

Description:
Alice creates a market with the question:
"Who will win the 2028 presidential election?"

An attacker front-runs Alice's transaction and creates a market with the exact same parameters.

Now, two markets with identical parameters are created simultaneously.

It becomes difficult for Kleros to determine which one is legitimate because both parties can argue in opposite directions:
"He front-ran me," or "He back-ran me."

In this case, unfair market creation can occur, and the attacker might win the dispute, as there is no clear way to identify which market is legitimate.

Recommendation
One solution I know of is to implement a simple off-chain mechanism that requires users to first submit a question along with their wallet address before creating a market. This can help prevent such issues.

[clesaege]

There is no problems in having similar/duplicate markets. If you believe there is, please show an example of something breaking for similar/duplicate markets.