New Strong Sell Stocks for August 31st: It's Not a List of the Biggest Losers

Every month, a fresh "Strong Sell" headline gets treated like a wall of shame for the biggest losers. That is a misread, and it costs people money in both directions: they assume a stock that already fell hard must be on the list, or they assume a stock that is ripping is safe because it is not. The flag is a mismatch detector, not a casualty list. The question worth asking is not "which names fell furthest," but "which prices are still out of sync with the fundamentals underneath them."

The mechanics are consistent, whatever scoreboard sits behind a Strong Sell rating: valuation, growth, profitability, momentum, and earnings revisions, each measured against the company's own sector and refreshed — my own framework re-ranks every trading day. A stock qualifies by showing the weakest collective score across those factors, not by how many points it lost. That is why one name can be newly flagged after a 50% drawdown, while a different one dodges the flag while its finances burn. Three names in late August show all three shapes.

CoStar (CSGP): down 52%, still priced like the old CoStar

CoStar is down about 52% year to date and roughly 64% over the trailing year, at $32.22. By any ordinary reading, the stock has already been punished. The factor screen's answer is that the punishment did not close the gap: CoStar still trades at roughly 176 times trailing earnings and about 39 times EV/EBITDA — richer than its chief rival Zillow on both price-to-sales (3.7x vs. 2.9x) and EV/EBITDA (39x vs. 28x). The price is still paying for the CoStar that used to run software-like margins.

The factor that broke is profitability, and it did not break from the top of the income statement. Gross margin is still near 79%; the operating margin has collapsed to about 2%. Full-year 2025 made the damage explicit: revenue up 19% to $3.2 billion, net income down to $7 million. Growth is not the problem — Q1 2026 revenue was up 23%, the company's 60th consecutive quarter of double-digit growth — which is exactly why this is a valuation-and-profitability mismatch rather than a dying business. The cost side is the Homes.com fight: CoStar poured a billion-dollar bet into competing with Zillow in residential listings, a war it has been dialing back as 2026 opened. In January it promised "meaningful moderation in net investment in 2026 and beyond" and announced a $1.5 billion buyback. By Q2, adjusted EBITDA had more than doubled year over year to $184 million.

Read that as a lagging flag. The rating still reflects the 2025 report card — 2% margins at a 39x EBITDA multiple — while management says 2026 is the inflection point. A refreshed rating exists precisely so a static label cannot hide that kind of divergence. The stock bounced 12% in the past month on early signs of that margin story; the factor case does not change until the margins do. CoStar stays out of the growth sleeve at this multiple, and the trigger to revisit is a couple of quarters of operating-margin recovery, not a price bounce. In our book, a D on profitability still fails, no matter how loud the turnaround narrative gets.

Moderna (MRNA): the flag's blind spot

Now the mirror image. On paper, Moderna's fundamentals are worse than CoStar's. Revenue was roughly $1.9 billion in a single quarter of 2024; Q2 2026 revenue was $145 million, down about 28% year over year and 63% sequentially. Operating margin is roughly negative 153% and gross margin about 22%; the company lost $1.97 per share in Q2. Yet at about $138 it carries a $55 billion market cap — roughly 25 times trailing sales — for a business that is shrinking. Expensive, unprofitable, and shrinking is textbook Strong Sell material on valuation, growth, and profitability.

The reason Moderna is not a straightforward flag is the timing factors running the other way. On August 19, Moderna and Merck reported a positive Phase 3 readout for a personalized melanoma vaccine, and the stock nearly tripled in a single session. It is up more than 350% in 2026 — momentum strong enough to suspend the flag. That is where process discipline matters most. Buying after a move like this is not a factor call; it is a binary bet that the vaccine franchise's revenue math arrives fast enough to justify the multiple. The giveback arrived just as fast — within days the stock gave back more than 20% of the spike. Even the aggregate scoring services have turned cautious on it: AInvest's composite signal is near-bearish even as the consensus label is Hold. Momentum is a timing tool, not a thesis. If this name is held at all, it is the small speculative side of a barbell, and the trigger to reassess is the next revenue and guidance refresh — not the chart.

The Trade Desk (TTD): when the price does the de-rating

The third shape is the one that trips investors the other way. The Trade Desk fell further than CoStar — down about 75% over the past year to $13.57 — yet on the valuation factor it no longer convicts. The shares trade at roughly 16 times trailing earnings and 6.5 times EV/EBITDA, with a 20% operating margin and a 28% free-cash-flow margin. The price did the de-rating. What still drags are the timing factors: momentum is dead — the stock sits below its 200-day average with an RSI near 37 — and the estimate track record is unproven, with EPS misses in each of the last two quarters and a revenue miss in Q2. The right reading is not "Strong Sell because it fell" but "revisions and momentum have not confirmed — wait for the reset." This is the case where assuming a fallen name must be on the list is exactly the mistake.

What the list teaches

Line the three up and the framework shows its own edges. CoStar is the flag working as designed: still rich where the fundamentals broke. Moderna is the flag's blind spot: momentum suspends it while the financials argue against the price. The Trade Desk is the flag's lag: cheaper, but unconfirmed. None of these is a "short everything" signal, and none is a "buy the dip." The disciplined use of this list is structural, not emotional: keep speculative conviction positions small, pair any single bet with a durable income or quality sleeve — rising uncertainty is answered with a barbell, not with louder predictions — and treat each name as a report card with a moving date. CoStar's is margin recovery. Moderna's is whether the vaccine franchise replaces the collapsing product revenue. The Trade Desk's is a genuine estimate reset. Watch the factors, and let the price follow.