MGM Resorts International
MGM disclosed a cybersecurity issue that forced system shutdowns and disrupted hotel and casino operations across multiple US properties.
-13.1% MGM vs -1.7% SPY
This site shows how share prices moved after an incident became public. It does not prove that the incident caused the move. Company news, sector moves and the wider market can affect every result. Educational only — not investment advice.
Disclosure timing
When could the market react?
The baseline is the last adjusted close before the news was public. The reaction session is the first close afterward.
- 01Baseline sessionSep 8, 2023
Normalized to 100 for both MGM and SPY.
- 02Public disclosureSep 11, 2023 · time unknown
Publication time is not documented; lower timing precision.
- 03First reaction closeSep 11, 2023
-2.4% company total return versus +0.7% for SPY; -3.0 pp market-relative return.
Disclosure time is unknown; the previous session close is used as baseline.
Time windows
Company vs SPY
Each row uses the last trading session on or before its target date. “Market-relative” is the company return minus the SPY return, in percentage points.
| Window | Endpoint | MGM | SPY | Market-relative | Signal |
|---|---|---|---|---|---|
| First reaction | Sep 11, 2023 | -2.4% | +0.7% | -3.0 pp | Below SPY |
| +7 days | Sep 18, 2023 | -7.9% | -0.1% | -7.8 pp | Below SPY |
| +1 month | Oct 11, 2023 | -13.1% | -1.7% | -11.4 pp | Below SPY |
| +3 months | Dec 11, 2023 | -0.5% | +4.1% | -4.5 pp | Below SPY |
| +6 months | Mar 11, 2024 | -2.5% | +15.6% | -18.1 pp | Below SPY |
| +12 months | Sep 11, 2024 | -19.1% | +26.2% | -45.3 pp | Below SPY |
Compare with current catalog aggregates
| Window | This case | Catalog median | Catalog mean | n |
|---|---|---|---|---|
| First reaction | -3.0 pp | -0.8 pp | -1.5 pp | 30 |
| +7 days | -7.8 pp | -2.0 pp | -4.0 pp | 30 |
| +1 month | -11.4 pp | -6.6 pp | -6.8 pp | 30 |
| +3 months | -4.5 pp | -5.1 pp | -6.6 pp | 30 |
| +6 months | -18.1 pp | -5.6 pp | -7.5 pp | 30 |
| +12 months | -45.3 pp | -3.7 pp | -10.1 pp | 30 |
Normalized total return
MGM compared with SPY
Baseline session = 100. Adjusted close reflects splits and reinvested distributions.
MGM Resorts International had -19.1% company total return versus +26.2% for SPY; -45.3 pp market-relative return. The chart shows normalized adjusted-close performance for up to 24 months.
View tabular chart fallback
| Date | MGM | SPY |
|---|---|---|
| Sep 8, 2023 | 100.0 | 100.0 |
| Oct 9, 2023 | 85.0 | 97.4 |
| Nov 7, 2023 | 87.5 | 98.4 |
| Dec 7, 2023 | 91.0 | 103.2 |
| Jan 9, 2024 | 102.0 | 107.2 |
| Feb 8, 2024 | 106.2 | 112.7 |
| Mar 11, 2024 | 97.5 | 115.6 |
| Apr 10, 2024 | 102.1 | 116.6 |
| May 9, 2024 | 93.4 | 118.0 |
| Jun 10, 2024 | 93.2 | 121.5 |
| Jul 11, 2024 | 104.8 | 126.7 |
| Aug 9, 2024 | 84.9 | 121.3 |
| Sep 10, 2024 | 79.7 | 124.9 |
| Oct 9, 2024 | 91.9 | 131.8 |
| Nov 7, 2024 | 86.1 | 136.0 |
| Dec 9, 2024 | 83.7 | 138.0 |
| Jan 10, 2025 | 72.9 | 133.0 |
| Feb 11, 2025 | 78.3 | 138.7 |
| Mar 13, 2025 | 69.0 | 126.3 |
| Apr 11, 2025 | 67.1 | 122.7 |
| May 13, 2025 | 79.8 | 134.8 |
| Jun 12, 2025 | 75.8 | 138.7 |
| Jul 15, 2025 | 86.2 | 143.4 |
| Aug 13, 2025 | 83.3 | 148.6 |
| Sep 11, 2025 | 80.8 | 151.5 |
Price recovery
Recovered
Here, recovery only means that adjusted close reached the baseline again. It does not mean every effect of the incident ended.
- State
- Recovered
- Initial trough
- -7.9% on Sep 18, 2023
- Recovery close
- Dec 13, 2023
- Calendar days
- 93
- Observation cap
- 24 months after disclosure
Hypothetical $1,000
What would $1,000 have looked like?
Compare $1,000 in MGM with $1,000 in SPY, bought and measured on the same dates.
Entry Sep 14, 2023 Exit Mar 14, 2024
Uses fractional shares and adjusted close. Leaves out taxes, fees and slippage. The holding period starts on the purchase date. This is a historical illustration, not an investment strategy.
Case note
MGM took systems offline after detecting a cybersecurity issue, affecting reservations, payments, gaming and other property operations. The company later said the event reduced third-quarter results and disclosed customer-data exposure.
Contemporaneous reports establish September 11 as the first public date, but the exact post time is not retained with sufficient confidence. The previous session close is therefore used under the lower-precision rule.
Evidence
Sources and case review
We qualify each case before checking its price results. These links support the disclosure date, listing, incident and business impact.
- primary Sep 12, 2023MGM Resorts International statement on cybersecurity issue MGM Resorts International Supports: Disclosure, Listing, Impact, Description
- secondary Sep 11, 2023Cybersecurity issue prompts computer shutdowns at MGM Resorts properties across US Associated Press Supports: Disclosure, Timing, Impact
- secondary Sep 11, 2023MGM Resorts takes systems offline as it investigates cyberattack Cybersecurity Dive Supports: Disclosure, Timing
- Listing evidenceChecked Jul 20, 2026MGM Resorts statement on cybersecurity issue MGM Resorts International The issuer statement and event-period filings identify MGM Resorts as NYSE: MGM.
Why it is included. MGM directly suffered a broad attack that disabled operational systems across US resorts and later reported a measurable revenue and cash-flow effect. Reviewed Jul 20, 2026.