How do I check a FiveM script for security?
Check whether every server net event validates the player's identity, permission, and argument types and ranges before acting, and whether it rate-limits repeated calls — a client can trigger any registered event with any payload, so unvalidated handlers are the root of most FiveM exploits. If source is open, grep for RegisterNetEvent/RegisterServerEvent handlers and read the first lines. If it's escrowed, test behaviorally: spam an interaction and watch for duplication or state you shouldn't reach.
In one lineChecking a FiveM script for security means verifying that every server-side net event validates the caller, checks permission, limits rate, and validates argument types before it changes state.
The longer answer.
Any player's client is hardware the server operator doesn't control, and cheat menus work by calling the same net events a script registered, with whatever arguments the attacker chooses — `TriggerServerEvent('shop:buy', item, -999999)` is the default attack, not an exotic one. A script is only as secure as its least-validated event handler, which is why security review starts at every RegisterNetEvent, not at the feature list.
A solid handler checks, in roughly this order: that the caller is a real, connected player in a state where the action is even plausible; that their job, grade, or permission actually authorizes it, read server-side; that the event isn't arriving faster than a human could trigger it; and that every argument is the type and range it claims to be, with amounts and rewards computed from server data rather than accepted from the client. Missing any one of these is a real, exploitable gap.
If source is available, a fifteen-minute pass is realistic: grep for RegisterNetEvent and RegisterServerEvent, read the first several lines of each handler for those checks, and search for database writes that trace back to a client-supplied number with no server-side clamp. If the resource is escrowed, test behaviorally instead — rapidly repeat an interaction and watch for duplication, try triggering an action from an invalid game state, and ask the seller in writing how they validate events, since a vague answer is itself the finding.
Common FiveM net-event attack vs. required defense
| Attack | What it exploits | Defense |
|---|---|---|
| Forged or out-of-range arguments | A handler trusting a client-sent amount or ID | Server-side type and range validation on every argument |
| Event spam | No rate limit on a valuable action | Per-player, per-event rate limiting server-side |
| Trigger without the precondition | No check that the action is actually possible right now | A server-tracked state machine gating the handler |
| Race or double-fire | Two rapid calls read the same state before either writes | Atomic check-and-set or a per-player lock around the mutation |
| NUI callback forgery | Treating a UI callback as inherently trusted | The same server-side checks as any net event, applied to NUI callbacks too |
The checklist.
- 01List every RegisterNetEvent/RegisterServerEvent in the open source and confirm each validates the player, permission, rate, and argument types before writing anything.
- 02Search for money, item, or reward amounts that reach a database write without a server-side clamp or lookup.
- 03Check that timers and progress bars are confirmed server-side, not just trusted from a client "finished" callback.
- 04For escrowed code, ask the seller in writing how they validate events, then test the demo by spamming an action and trying it from an invalid state.
- 05Confirm SQL uses parameterized queries, not string concatenation, anywhere player-controlled text reaches the database.
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Published 2026-09-02 · Last reviewed 2026-09-02 · Vice Drip · All answers